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7/30/2019 Ltg5372.Tmp - US Army http://slidepdf.com/reader/full/ltg5372tmp-us-army 1/24 FM 31-71 CHAPTER 3 COMBAT AND COMBAT SUPPORT Section I. 3-1. General a. The role of infantry in northern operations remains essentially the same as in other climates, although the technique of accomplishing a mission may vary considerably. Units usually are organ- ized into highly mobile, self-sustained tactical groupings with only those weapons and equipment suited to the operation. b. The value of surprise is greatly increased in forested areas under conditions of cold and snow. Skillful use of weather conditions, such as fog or blowing snow, can be of great advantage. To in- sure success, plans for infantry operations must be made in detail and be made known to every individual before action is initiated. 3-2. Cover and Concealment a. In the forested areas, troop movements are concealed by the trees. Cover from hostile fire may be constructed from existing timber, by dig- ging emplacements, and the use of icecrete, snow, and ice. Log and snow covered bunkers may be used for additional protection. b. In the treeless barren lands, few recognizable terrain features exist. Observation will, at times, be aided by the extreme clarity of the air. In the open tundra and barren lands of the Arctic, the ground is permanently frozen except in some sand and gravel areas, raised beaches, or lakes and river banks. Even here, frost often lies within a few centimeters of the surface. Consequently, the siting, construction, and concealment of defense positions are more difficult than farther south. In winter, snow normally is the only construction material, but fortunately deep hard-packed drifts usually are associated with tactical features. Even during the summer, it will often be difficult to dig in because of permafrost and poor drainage. Ad- vantage must be taken of every natural object and surface depression which will provide any degree of cover and concealment. Breastworks may be INFANTRY built by using peat rocks, surface gravel, clumps of soil, and vegetation. Because of the difficulties of concealment, dispersion and deception must be practiced. During these periods, units must use caution in their movements, as the advantage will lie with the observer who can remain motionless. 3-3. Effect of Terrain on the Accomplishment of the Infantry Role Terrain and climate combine to decrease mobility of infantry units. In summer, muskeg swamps and lakes form barriers which must be sur- mounted or bypassed. When frozen, lakes, swamps, and rivers may often be used as roads. 3-4. Effect of Cold on Infantry Weapns (TM 9-207) a. In extreme cold, metal becomes brittle. In- creased parts breakage occurs in all types of weapons. b. Many weapons create ice fog which, on a still day, may obscure the gunner’s vision; thus requir- ing movement to alternate positions or the use of a flank observer to direct the fire. c. Mortars experience an increase in breakage of firing pins and cracking of base plates. When ground mounted mortars are used, the base plates must be cushioned against the frozen ground by using sandbags, small branches or bushes, ever- green boughs, small logs or similar type material which will provide a suitable cushion. Precautions must be taken to prevent the mortar mount from becoming frozen to the ground, and the power supply for aiming past lights should be secured in a warm tent or shelter. d. Experience firing data should be used for recoilless rifles and rocket launchers, and back blast areas must be increased to compensate for the slower buring propellant. Rocket launcher gunners must wear the, face mask for protection from the flying particles of propellant. 3-1

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    CHAPTER 3

    COMBAT AND COMBAT SUPPORT

    Section I.

    3-1. General

    a. The role of infantry in northern operationsremains essentially the same as in other climates,although the technique of accomplishing a missionmay vary considerably. Units usually are organ-ized into highly mobile, self-sustained tacticalgroupings with only those weapons and equipmentsuited to the operation.

    b. The value of surprise is greatly increased inforested areas under conditions of cold and snow.Skillful use of weather conditions, such as fog orblowing snow, can be of great advantage. To in-sure success, plans for infantry operations mustbe made in detail and be made known to everyindividual before action is initiated.

    3-2. Cover and Concealment

    a. In the forested areas, troop movements areconcealed by the trees. Cover from hostile firemay be constructed from existing timber, by dig-

    ging emplacements, and the use of icecrete, snow,and ice. Log and snow covered bunkers may beused for additional protection.

    b. In the treeless barren lands, few recognizableterrain features exist. Observation will, at times,be aided by the extreme clarity of the air. In theopen tundra and barren lands of the Arctic, theground is permanently frozen except in some sandand gravel areas, raised beaches, or lakes andriver banks. Even here, frost often lies within afew centimeters of the surface. Consequently, thesiting, construction, and concealment of defense

    positions are more difficult than farther south. Inwinter, snow normally is the only constructionmaterial, but fortunately deep hard-packed driftsusually are associated with tactical features. Evenduring the summer, it will often be difficult to digin because of permafrost and poor drainage. Ad-vantage must be taken of every natural object andsurface depression which will provide any degreeof cover and concealment. Breastworks may be

    INFANTRY

    built by using peat rocks, surface gravel, clumpsof soil, and vegetation. Because of the difficultiesof concealment, dispersion and deception must bepracticed. During these periods, units must usecaution in their movements, as the advantage willlie with the observer who can remain motionless.

    3-3. Effect of Terrain on the Accomplishmentof the Infantry Role

    Terrain and climate combine to decrease mobilityof infantry units. In summer, muskeg swampsand lakes form barriers which must be sur-mounted or bypassed. When frozen, lakes,swamps, and rivers may often be used as roads.

    3-4. Effect of Cold on Infantry Weapns(TM 9-207)

    a. In extreme cold, metal becomes brittle. In-creased parts breakage occurs in all types ofweapons.

    b. Many weapons create ice fog which, on a stillday, may obscure the gunners vision; thus requir-ing movement to alternate positions or the use ofa flank observer to direct the fire.

    c. Mortars experience an increase in breakageof firing pins and cracking of base plates. Whenground mounted mortars are used, the base platesmust be cushioned against the frozen ground byusing sandbags, small branches or bushes, ever-green boughs, small logs or similar type materialwhich will provide a suitable cushion. Precautionsmust be taken to prevent the mortar mount frombecoming frozen to the ground, and the power

    supply for aiming past lights should be secured ina warm tent or shelter.

    d. Experience firing data should be used forrecoilless rifles and rocket launchers, and backblast areas must be increased to compensate forthe slower buring propellant. Rocket launchergunners must wear the, face mask for protectionfrom the flying particles of propellant.

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    e. Special care should be taken to avoid touch-ing metal parts of weapons with exposed skin.This is especially true when an individual assumesa firing position and the side of the face contactsthe weapon.

    3-5. Effect of Ice and Snowon Infantry Weapons (TM 9-207)

    a. Infantry weapons will function under north-ern conditions when men have been trained intheir proper maintenance, lubrication, and use.

    b. The main problem is to keep snow and ice outof the working parts, barrels, and sights. Specialbreech and muzzle covers should be provided andtroops trained in their use. Special light lubri-cants are necessary because of the effect of cold onnormal lubricants.

    c. As a result of bringing a weapon into a warmshelter, condensation or the melting of accumu-

    lated snow may occur which will cause it to freezeand malfunction when taken back into the outsidecold temperatures. This condition can be pre-vented by leaving the weapons outside, underguard, or thoroughly cleaning them inside theshelter.

    3-6. Environmental Effect onInfantry Operations

    a. Infantry operations may become restrictedbecause of limited roads and lines of communica-tion. Terrain is less accessible in all seasons than

    in temperate zones. Troops require more time todevote to problems of living and shelter duringwinter months. Efforts must be directed towardoversnow mobility. Infantry must not becomeroad bound. The guiding principle in providingequipment for infantry should be to provide only

    the minimum amount consistent with the healthof the troops and the success of the mission.Snowshoes or skis are essential for individualmovement; and sleds must be provided for eachsmall group to carry tentage, stoves, fuel, andother equipment necessary for sustained combat.Consideration of mountainous terrain and gla-ciers is treated in FM 31-72.

    b. In attaining individual mobility, the primaryconsideration is how much a man can leave behindwithout impairing his capability as a combat sol-dier. Only ammunition and indispensable items,including lightweight rations and existence loadsshould be carried. Items not necessary for fightingor survival are transported in unit trains.

    c. Because of the dampening effect of deep snowor mud, impact bursts of artillery and mortars areless effective. Mines often fail to explode whenstepped on or when driven over by tanks. The useof such weapons, accordingly, is weighed carefully

    in the light of the specific requirements of eachoperation. A plentiful supply of ammunition for afew weapons is more desirable than a wide vari-ety of weapons with little ammunition.

    3-7. Tactical Considerations

    (Detailed operations are covered in chap 2.) Thesituation will dictate the tactical composition ofthe forces. The factors of METT (mission, enemy,terrain and weather, troops) and fire supportavailable, govern the tailoring of task forces. Theattachment and detachment of units is ideally

    suited for northern operations. The use of airmo-bile forces for deep penetrations gives the com-mander greater flexibility in the formulation ofhis operational plans, and should be considerednormal ratherareas.

    Section II. ARMOR UNITS

    3-8. The Role of Armor Units mount to tank

    a. The mission of armor units in northern lati-problem.

    tudes, as elsewhere is to attack, disrupt, and de-

    stroy enemy forces by fire, maneuver, and shockeffect. Maneuver is limited to deep snow and ex-treme cold in winter and by the vast areas ofmuskeg in the summer. Firepower and the shockeffect of tanks against unprotected personnel is asdemoralizing in the areas of northern operationsas in any other area.

    b. Terrain and trafficability studies are para-

    than special operations in northern

    employment since trafficability is a

    c. Employment of tanks in elements of platoons,

    companies, and battalions as part of a combinedarms task force is desirable, especially in sus-tained operations.

    3-9. Effects of Deep Snow

    a. It is impractical to establish definite rules forthrough-the-snow operations due to the variedconditions encountered. Since experience in each

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    particular area is necessary to accurately predictsnow trafficability, reconnaissance must be madefor each separate action to determine currentsnow conditions. Most tracked vehicles are slowedby 60 to 75cm (24 to 29) of wet snow. Heavytracked vehicles may negotiate fine, dry snow of lto 2 meters (3 to 6) in depth. Normal speedsmay be maintained after a packed snow trail has

    been formed by the passage of several heavy vehi-cles. The surface of a packed snow trail becomescompacted into a hard mass resembling well-packed wet sand and is easily traversed by alltypes of vehicles. In the event of thaw, properdriving techniques must be used to prevent vehi-cles from tracking and eventually becomingmired. Freezeups frequently follow thaws, andproduce glare ice which makes roads practicallyimpassable to tracked vehicles, particularly onslopes of 35 percent or greater. Again, properdriving techniques must be emphasized as it isdesirable that all vehicles track the lead vehicle on

    glare ice. Tracklaying vehicles operating in thenorth should be equipped with all steel chevrontracks for all season cross-country operations.

    b. Dry snow causes few operating difficulties asit has little tendency to pack on suspensions sys-tems. Wet clinging snow has a tendency to accu-mulate on the tracks, suspension idler wheels, andsprockets, and may require occasional halts forremoval.

    3-10. Ice CrossingLakes and streams may be crossed on the ice dur-ing the winter months if ice is of sufficient thick-ness and reasonable precaution is exercised.Crossing sites must be inspected for cracks, pres-sure ridges, and thin spots prior to placing vehi-cles on the ice (table 2).

    3-11. During Spring Breakupa. Vehicles mired in deep frozen mud or ice

    require special recovery techniques. Tanks shouldbe parked on high dry ground, unthawed snow, oron brush or logs to prevent freezing in. Duringthe breakup as the active frost layer begins to

    melt the ground becomes soft and marshy. Al-though traction is poor, operation is possible dur-ing this period if tanks can penetrate the mud andfind footing on the frost layer below. As the sea-son progresses, the active layer thaws and as ve-hicles sink deeper into the muck they may bellydown and become immobile. To provide greatermobility under these conditions, vehicles shouldnot follow in the same tracks of preceding vehi-

    cles. Movement is possible in areas where perma-fost is still near the surface, i.e., on the shadedside of woods, on ground with a good moss cover,and on the shaded slopes of hills. Even when thevalleys have become impassable, limited operationmay still be possible on crests where drainage isbest.

    b. Extreme caution is necessary in crossinglarge streams and lakes early and late in the coldseason.

    3-12. During FreezeupConditions during the early freezeup are much thesame as those which occur in the spring. Theground thaws in the daytime and freezes at night.When the frost comes to the surface and theground is completely frozen, a period of high mo-bility for the tank is experienced. The frozenground offers good footing, and the shallow snowdoes not effectively reduce the speed of the tank.

    Frozen ruts, especially during early fall, are ahazard. Stream and lake ice cannot be used forcrossing; however, many can be forded by break-ing through the thin ice. In areas with fewstreams, the late freezeup season offers the bestopportunity for tank employment.

    3-13. Summer Movement

    a. In summer, much of the northern terrain is asoft mud-based marshland or muskeg, or is aswamp that is covered with a thin layer of mossand lichens. Once the moss layer is ruptured, the

    mud offers no support above the permafrost level.In some areas during summer, the frost layer re-cedes to a depth that limits tank operations.Floating bogs may also be encountered. Thesefloating bogs are masses of thickly matted vegeta-tion and rotting vegetable matter that float onpools of water. They are difficult to locate by nor-mal inspection as they usually will support a man;however, they will often not support even thelightest vehicles. If a floating bog is suspected, along probe pole should be used to determine wherethe bog lies. Muskeg should be avoided by carefulreconnaissance and route selection. In some locali-

    ties, muskeg is interspersed with large glacierboulders just below the surface. Damage to sus-pension systems and tracks is highly probableduring operations in such terrain.

    b. When it becomes necessary to cross openmuskeg, vehicles should not follow in the sametrack. In very soft spots, each vehicle shouldmake its own track. No abrupt turns should be

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    attempted. Recovery in muskeg is exceptionallydifficult because tanks belly down and tracksdo not regain the surface. It is frequently neces-sary to winch the tank to a spot where the mus-keg is solid enough for the tracks to regain thesurface before recovery can recompleted. Seldomcan recovery be accomplished with less than twoadditional vehicles.

    3-14. Preparation for Winter Operations

    The commander is responsible for insuring thattanks and other equipment are completely winter-ized in accordance with the pertinent lubricationorder (LO), with TM 9-207 for added informa-tion, to insure use of correct materials prior tothe advent of cold weather. Failure to winterizetanks will render them inoperative in cold or ex-treme cold. Winterization of equipment should beundertaken on a priority basis. Units embarkingfor the north during the winter months should

    have all winterization completed prior to depar-ture in order to be operational immediately uponarrival. Tank crews should be provided withsnowshoes, tents, and heating equipment.

    3-15. Observation of Fire

    a. Visibility in the north, as it affects tank gun-nery, presents many problems. The formation ofice fog, blowing snow, snowfall in driving winds,and snow blown up by muzzle blast all reducevisibility. Soft snow blown by the muzzle blastwill probably exist under any condition where

    light dry snow is on the ground. The burningpropellant will create ice fog. The explosion of ahigh explosive shell will create a similar conditionin the target area. Masses of dry snow are alsoblown into the air by the burst. First round hitsassume even greater importance. When these con-ditions cause the gunners vision to be obscured,observation from another tank maybe the quick-est means of adjusting fire. The tank commander,because of his elevated position and the availabil-ity of magnifying sights and field glasses, hasmuch better visibility and depth perception onsnow covered terrain than have troops on the

    ground.

    b. Extreme cold decreases muzzle velocity andhence the accuracy of tank ammunition. Correc-tions for firing table data and for ballistic com-puter setting must be furnished by ordnance fortypes of ammunition issued in the northern lati-tudes. If these corrections are not furnished, thenusing units must determine them by actual firing.

    3-16. Handling of Tank Ammunition

    Certain difficulties in handling ammunition arepresent. The binding tape around the fiber cartonis difficult to remove while wearing mittens; am-munition cannot be touched with the bare handswithout danger of metal burns. Ammunition tendsto freeze in the wooden fuze-protective-ring, mak-ing it necessary to cut ammunition from the fibercases. Cold ammunition placed in the warm inte-rior of a tank will grow frost crystals if thetank interior is even slightly warmer than theouter air. These crystals increase the difficulties ofammunition handling. Ammunition racks are dif-ficult to operate while wearing mittens; however,operation is expedited by the use of leather thongsor extensions on rack latches and other handles.

    3-17. Operations in Extreme Cold

    a. Crew Comfort. Tank compartments are morecrowded and entry and exit through hatches ismade more difficult by heavy clothing necessaryfor northern operations. Confined crew positionsin tanks cause parts of the body to becomecramped, thereby restricting circulation. In theseconfined positions, clothing is drawn tight or be-comes compressed and loses its insulation value.The drivers and commanders are subject to in-creased windchill as they are frequently requiredto ride with their heads outside the hatches and areexposed to the wind generated by the movementof the tank. Constant supervision is necessary toinsure against frostbite. Halts, regulated to fit the

    situation, must be made. Personnel must be re-quired to dismount and move around to restorecirculation, and warm body parts chilled by lossof insulation and to rotate crew positions. Wind-breaks should be used during movement in ex-treme cold to reduce the windchill factor.

    b. Tank Operations. After the tank engine isstarted and warmed up, the tank should move outslowly. The power train should be broken loosegently to prevent failures due to sudden shock.Sharp turns should be avoided until the transmis-sions and differentials have had time to warm up.Initial movement should be restricted to low gear

    operations for some distance until final drives,wheels bearings, and support rollers have becomefree. At each halt, packed snow should be removedfrom the suspension and drive sprockets to pre-vent track throwing.

    c. Avoid Exploring. Avoid driving in deepsnow, snowdrifts, or on ice unless the route isprescribed and reconnoitered or the mission re-

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    quires it. Plunging through woods is dangerous astops of frozen trees may break off and fallstraight down on the tank. If necessary, treesshould be pushed down slowly and cautiously withthe tank hatches closed.

    d. Carbon Monoxide. Crews must remain con-stantly alert for carbon monoxide. Open flame

    heaters or engine exhaust must not be used toheat closed areas.

    e. Vehicle Starting.(1) Vehicles should be exercised frequently

    to prevent the power train from becoming coldsoaked. Engines not equipped with external en-gine heaters should be started periodically to keeplubricants and engines warm.

    (2) Frozen power trains and engines of ex-tremely cold vehicles are easily damaged by tow-ing in attempts to start these vehicles. In manycases, it is impossible to start track vehicles bytowing because the suspension and final drives areso cold that the tracks will not rotate. Extremecare must be used in towing or pushing to insurethat no sudden shocks are applied. Metal is verybrittle in cold; tow cables, final drives, or pushbars may fail under shock loads. However, an en-gine may be started by towing ifno other meansof starting is possible.

    3-18. Maintenance in Extreme Cold

    a. Maintenance Difficulties. Maintenance of me-chanical equipment in extreme cold is exception-ally difficult in the field. Shop maintenance time is

    also increased because equipment must be allowedto thaw out and warm up before repair can beaccomplished. Extreme care must be exercised inperforming maintenance in extreme cold as barehands will stick to cold metal. Also, fuel in contact

    3-19. Field Artillery, General

    a. Artillery fire support will

    Section III.

    be provided innorthern operations as in other areas. However,

    artillery units will find that problems of mainte-nance, mobility, resupply, observation, survey,and communications are intensified.

    b. (1) The rugged and inaccessible nature ofthe terrain may require the use of self-propelledand air mobile artillery. Normally, a light towedartillery battalion (some terrain may dictate SPartillery) will be attached to an infantry brigadeemployed as a task force. Medium or heavy artil-

    FM 31-71

    with the hands will result in supercooling due toevaporation, and hands can be painfully frozen ina matter of seconds. For detailed maintenance in-structions see TM 9-207.

    b. Time Required to Perform Maintenance. Attemperatures below 40 F., as much as fivetimes the normal maintenance time may be re-

    quired. Starting and warmup time is also in-creased, and may approach 2 hours in tempera-tures of 50

    o

    F. Complete winterization, diligentmaintenance, and well-trained tank crews are nec-essary in winter operations. The degree to whichcold affects operation can be stated in three gen-eral temperature ranges.

    (1) Down to 100

    F., operation is not diffi-cult, but resembles operation in the northern por-tion of the United States during the hardestwinters.

    (2) From 100

    F. to 400

    F., operations are

    more difficult. At the warm end of the range, lackof winterization will result in only a slight loss inefficiency; at the bottom of the range, lack of win-terization and training will result in many fail-ures.

    (3) Below 400F., operations become in-

    creasingly difficult; at temperatures in the vicin-ity of 60F., the maximum efforts of well-trained men are required to perform even a sim-ple task with completely winterized materiel.

    c. Maintenance Shelter. Performance of fieldmaintenance at temperatures of below 20

    0

    F., is

    extremely difficult unless some type of heatedshelter is provided. Maintenance shelter tents,portable shelters, or large tarps and air duct heat-ers are necessary whenever tanks are operated inthe northern latitudes.

    ARTILLERY

    lery, airmobile artillery or rockets may be em-ployed for additional fire power and a nuclearcapability.

    (2) Glacier and mountain operations may re-quire the employment of air mobile artillery.Units assigned such a support mission may beequipped with supplementary weapons in order toaccomplish the task. Personnel must be thor-oughly trained in the techniques of loading, lash-ing, rigging, palletizing, and airmobile tactics.

    c. The artillery of a task force employed innorthern operations must be prepared to assume

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    functions, such as counterbattery, normally per-formed by a higher headquarters.

    d. MTOE must be augmented with cold weatheroperational equipment as necessary. If it is to beused in winter operations, all equipment should bewinterized prior to its arrival in the theater.

    e. Training and fire control at battery levelshould be emphasized. Training for northern op-erations should be accomplished prior to commit-ment of units whenever possible. Special emphasismust be placed on the problem areas inherent dur-ing cold weather operations. Personnel must alsobe thoroughly indoctrinated in the use of field ex-pedients for both summer and winter use.

    3-20. Field Artillery Movement

    a. Successful movement is accomplished as aresult of careful, detailed, and comprehensiveroute reconnaissance. Extensive reconnaissance,

    both air and ground, should be carefully consid-ered in great detail prior to any operation.

    b. (1) Winter is the best time of the year forcross-country movement in the area of northernoperations. However, problems are often encoun-tered in crossing certain rivers and muskeg areaswhich do not freeze even at temperatures of 50F. Ice thickness and load bearing capacity mustalways be determined prior to crossing frozenlakes and rivers. Bulldozers or vehicles withblades will be required to break trail for cross-country movement during winter months. For

    load-bearing capabilities of ice, see table 2.(2) During the summer months, movement

    across the extensive muskeg is severely restricted.Engineer support must be relied upon.

    c. The problem of determination of location andorientation while moving is increased due to thelimited map coverage and difficult terrain. Inmany cases, vehicle column movements can onlybe oriented by the column commander dismount-ing and determining direction with a compass.Artillery weapons used in airmobile operations re-quire tracked prime movers for linkup operations

    and further commitment.d. In order to obtain a cross-country capability

    in this area of practically nonexistent road net-works, it may become necessary to replace someof the wheeled vehicles with tracked vehicles inthe maintenance, survey, reconnaissance, andcommunication elements.

    e. The artillery must have the same mobility as

    the supported unit. This includes appropriatetraced vehicle transportation and proficiency inthe use of snowshoes and skis, particularly for theforward observers and liaison personnel. Armyaircraft can assist in maintaining direction, deter-mining location, reconnaissance, communications,and observation of fire.

    f. During winter movement, protection must begiven to personnel traveling in vehicles and forthose remaining with disabled vehicles. Facemasks and protective clothing for all drivers andassistant drivers not in heated cabs are manda-tory. Vehicular heaters, both engine and person-nel must be carefully maintained and a sufficientquantity of heater repair parts should be on handat the unit level. Loading plans should reflect thepresence of equipment such as tents, stoves, etc.,on each vehicle.

    g. Since artillery is faced with large bulk and

    weight resupply problems, maximum use of aerialresupply should be planned. Continuous exploita-tion of the tracked vehicle capability for resupplypurposes is necessary to insure the accomplishmentof the mission. All batteries should carry an emer-gency POL supply with them for use when and ifthey are separated from their parent battalion.

    h. Constant and energetic emphasis on motorand vehicle maintenance is required. The abnor-mal effects of low temperature upon vehicle mo-tors and equipment becomes a matter of primeconcern. During extreme cold, it may be necessaryto run engines and exercise all vehicles at fre-quent intervals to prevent cold soaking.sive leadership and command supervisiontial to insure operation and movement.

    3-21. Field Artillery Position Areas

    Aggres-is essen-

    a. Positions should be chosen primarily for tac-tical employment. However, consideration shouldbe given to locations affording protection from theelements. Areas should be prepared prior to occu-pation whenever possible. Parapets and gun posi-tions often must be built up with snow and availa-ble brush and wood rather then being dug in.Effective and continuous operation requires theestablishment of warming tents or shelters withinthe position area.

    b. Camouflage is difficult but not impossible.Maximum use should be made of camouflagepaint, lime, and available terrain features. Unitsshould be dispersed and camouflage discipline con-stantly enforced. The operation of vehicles, per-

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    sonnel heaters, stoves and the firing of weaponscan cause ice fog which discloses unit locations.Periodic displacement to alternate positionsshould be accomplished whenever possible.

    3-22. Field Artillery Observation

    a. During winter months, good observation is

    limited to a few hours each day because of theshort periods of daylight. Observation will also belimited during periods of fog, ice fog, snow-storms, and blowing snow. Snow cover reducesdepth perception and obscures ground featuresand landmarks. Amber filters for observation in-struments are required to improve visibility andreduce eye strain. Personnel operating these in-struments should be relieved frequently.

    b. Ground bursts are difficult to observe on snowcovered terrain and in muskeg due to the dampen-ing effect. Preliminary adjustment by airbursts or

    use of colored smoke may be required.c. Difficulty in determination of location will

    require use of special techniques to bring initialfire into the target area. Observers will often berequired to navigate by dead reckoning for orien-tation and for locating targets. The use of polarcoordinates to locate the target is common. Resec-tion from orienting rounds is one method that canbe used to assist the observer in determining hislocation. Safety of friendly troops must be care-fully considered at these times.

    d. The use of aircraft for observation should be

    exploited to the maximum. Light aircraft or heli-copters should be assigned or attached to the artil-lery for observation purposes. Such aircraft canalso assist in establishing communication relays,reconnaissance for routes and positions, identifi-cation of objectives, and for orienting groundtroops in addition to adjusting artillery fires.

    e. Observers must be equipped to move with thesupported elements. Special consideration shouldbe given to the radio equipment to be used by theobservers. The weight of radios, batteries, andother equipment becomes critical if the observers

    are required to use skis or snowshoes as a meansof transportation while attached to the infantryelements.

    3-23. Target Acquisition

    a. Traverse type survey is impractical over ex-tended distances. Instrument fog-up and othermechanical failures are experienced. Recordingand computing under winter weather conditions

    are extremely difficult. Survey control and ade-quate maps are seldom available. Grid azimuthsmay be determined by astronomic observation orby using a gyroscopic direction determining in-strument. Starting coordinates will often have tobe assumed. Triangulation usually is more feasi-ble than traverse.

    b. Use of helicopters to transport survey partiesto inaccessible locations and to mark stations fortriangulation may be necessary.

    c. Electronic distance measuring devices are themost practical means of carrying survey over ex-tended distances.

    d. As meteorological data is a requirement,metro sections may have to be equipped withtracked vehicles in order to accompany the for-ward elements during task force operations.Metro section operations pertaining to the collec-tion of data differ very slightly from those experi-

    enced in other areas.

    3-24. Field Artillery Delivery of Fire

    a. Normal fire direction procedures and tech-niques are valid during northern operations. Cer-tain procedures must be emphasized because theyare encountered more frequently in the north thanin temperate zones. Due to increased communica-tions difficulties, extended areas, and separatetask force operations, individual firing batterieswill be required to control their own fires morefrequently than in other areas.

    b. In most areas, survey control will be scarceor unavailable, therefore, it is often necessary tofire from an observed firing chart.

    c. Due to poor visibility, shortened daylighthours in the winter, ice fog, dense brush, andwooded areas, high burst registrations arecommon. In the situation where survey control isnot available, units may be required to register byestablishing a base and firing high burst registra-tions from the howitzer positions.

    d. During the long periods of darkness during

    the winter, aiming post lights are continually re-quired. To insure their operation during cold peri-ods, the power supplies for the lights should belocated in warm tents or shelters and remoted tothe lights.

    e. Extreme cold weather will affect the ballisticcharacteristics of the weapons and ammunition,the most significant of which is a reduction inrange. K factors of 100 meters per 1000 meters

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    (100 yds per 1000 yds) of range are not uncomm-on. Great care must be taken when firing theinitial round to assure clearance of friendly posi-tions. Whenever possible, metro plus velocityerror (VE ) techniques should be used. When ametro message is not available, known or esti-mated experience factors regarding range Kshould be utilized. If any doubt exists as to what

    range K can be expected, high burst techniquesmay be utilized to determine the point of impactof the initial round.

    f. Special care should be taken when selectingfuzes. This will vary with the type of target areaterrain. Keep snow and unfrozen muskeg willreduce the effect of impact bursts by as much as80 percent. Fuze time and variable time (VT) areparticularly effective against personnel in theopen. Some types of VT fuzes will malfunctionwhen temperatures are below 0F. When possible,these fuzes should be warmed by placing them

    inside the gun carriages (self-propelled), primemovers, special warming tents, or shelters con-structed from gun tarpaulins. Low temperatureswill also cause malfunctioning of illuminatingrounds by the freezing of the parachute and itscomponents. Warming of these rounds willgreatly reduce this probability.

    g. Chemical munitions are adversely affected bydeep snow. The canisters from base ejection shellsmay be smothered in the snow. Phosphorousshells, although producing the desired smoke, con-taminate the area of impact with phosphorous

    particles which remain buried in the snow.h. The field artillery digital automatic computer

    (FADAC) is capable of operating in extremes ofcold ranging to 25

    0F. with the addition of the

    back over this temperature can be lowered to40F. Extreme care should be taken by allowinga gradual warmup period to decrease the condensa-tion that occurs when a cold soaked machine isbrought into a warm humid room or tent. If tem-peratures are not exceedingly cold, the machinecan be turned on immediately upon entering aroom or tent thus decreasing the possibility of

    condensation by allowing rapid heating of inter-nal circuitry. The back cover should be left on themachine during this warming period. All switchesand buttons on the front panel of FADAC areconcave in design to facilitate them being oper-ated by pressing with a pencil rather than remov-ing the Arctic mittens and increasing the possibil-ity of frostbitten fingers.

    3-25. Field Artillery Communications

    a. Wire and radio nets used in temperate zonesare valid in the north and require no expansion.Due to difficulty of laying and maintaining exten-sive wire lines, radio normally is used as the pri-mary means of communications. However, thisdoes not imply that there should be any relaxation

    in the attempt to establish wire nets in the shor-test time possible in order to back up the existingmeans of communication. If available, an internalradiowire integration system should be estab-lished. The utilization of track-mounted VHFequipment will reduce the serious communicationproblems faced by the artillery.

    b. Since cold weather reduces the battery lifeand the operating range of the small man-carriedforward observer portable radios, a requirementoften exists for a relay between the firing ele-ments and the forward observers (FO). Use ofArmy aircraft may be exploited for this purpose.

    However, this method is less desirable thanground stations during extended operations.

    c. Communication problems encountered innorthern operations and their solutions are dis-cussed in detail in chapter 6.

    3-26. Air Defense Artillery

    a. Air defense artillery missions in northernareas are the same as those in other areas, subjectto modification of techniques caused by climate,terrain, and nature of the operations. Lack ofroads may reduce mobility and make resupply op-erations more difficult. Cold weather causes longerwarmup times for electronic equipment, use ofspecial heating devices for ready missiles, and, inair defense missile units, may require launchers tobe exercised at frequent intervals. Helicopter liftcapabilities should be considered for resupply. Innorthern latitudes the intense cold, with its at-tendant unpleasantness and complicated livingconditions, aflects military operations but doesnot stop them.

    b. The type of air defense artillery units em-ployed in northern operations are dictated by mis-

    sion, terrain, and available transportation. MTOEoften must be augmented to accomplish the as-signed mission. Winterization and modification ofequipment where necessary should be accom-plished prior to entrance into a northern area.Special clothing is required due to two types ofcold encountered: Wet-cold and dry-cold.

    c. Air defense artillery positions should be se-

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    lected for their tactical utility and considerationof the logistical factors involved. Air defense miss-ile units should, if possible, occupy previouslyprepared positions. Light air defense artilleryweapons mounted on full track vehicles mayoccupy hastily prepared positions and effectivelyaccomplish their mission. In adverse terrain, or

    under winter conditions, it maybe difficult to dig inpositions. Explosives may be used to expediteprotection of the position, or parapets may bebuilt up from logs or ice and snow. Alternate posi-tions should be chosen early and prepared as timepermits. Siting of air defense artillery such asNike Hercules system in arctic terrain is the sameas anywhere else. Movement during wintermonths is not impossible but is impractical. Formost efficient operation, previously prepared posi-tions must be used. Level and orientation is af-fected by earth tremors that occur frequently inthe northern part of the North American Conti-

    nent. During spring thawing, leveling would haveto be done several times daily due to permafroston other than solid rock foundations.

    d. Both friendly and enemy forces may useaviation to overcome scarce road network,strengthen signal communications, improve targetacquisition, and to move and support small units.As forward area weapons units become available,they may be used to provide protection againstaircraft. For use of nonair defense weaponsagainst aircraft see paragraphs 6-35 through6-38.

    e. Surface-to-air missile units using nuclearwarheads provide protection from any high alti-tude threat. Due to the electronic equipment forair defense artillery fire control systems, person-nel must attain a high state of training to per-form efficiently in the north. Heated shelters willbe required for maintenance personnel to performtheir duties. Generators, fire control equipment,and launching equipment must be operated at fre-quent intervals during periods of extreme cold.

    FM 31-71

    The effects of extreme cold on cables require thatthey be heated before coiling and uncoiling. Cableheads, plugs and connectors must be kept dry andfree of snow. Metal becomes brittle when cold andeven a slight jerk or blow may cause a pin toshear or a hook to break.

    f. Commanders whose force includes Nike Her-

    cules missiles should not neglect the secondaryground support capability of these weapons.

    (1) Muskeg and tundra areas afford suitablelanding sites to ski equipped aircraft during thewinter, with some engineer effort. A good recon-naissance must be conducted to detect the pres-ence of clumps of vegetation, rocks, and otherhazards to landing. Movement of aircraft andground handling of equipment is extremely diffi-cult in these areas.

    (2) Snow covered glaciers make suitablelanding fields for ski equipped aircraft. Ground

    reconnaissance should be made prior to landing.Crevasses, often hidden by snow, constitute athreat to any movement on glaciers.

    (3) When ice floes are solid enough in winter,they can be used for landing ski-equipped air-craft. Solidity of an ice flow can be judged fromthe air by the color of the ice. Dark patches indi-cate near-surface water showing through. Thesepatches make the ice floe too thin and unsuitableas a landing area. This color factor can also beused to judge the safety of frozen lake or riversurfaces. The thickness of the ice above the wateris another indication of the solidity of a floe. How-ever, this thickness can vary from 8 to 25 cm (3to 10) depending on the type of ice composingthe floe.

    (4) In a fixed wing landing on either a floe orfrozen lake surface, the pilot should lay a set oftracks on the intended landing surface by makinga touch and go landing. A visual reconnaissance isthen made of the tracks; any discoloration indi-cates that the landing surface is too thin for theairplane.

    Section IV. ARMY AVIATION

    3-27. General the same as for normal operations, however, the

    Army aviation missions do not change when oper-effects of terrain and weather require the use ofspecial equipment and modification of training

    sting in northern areas. The increased difficulties programs. A summary of weather and terrain isin surface transportation as opposed to the flexi- covered in other portions of this manual. Thisbility of air transportation will create increased section deals only with Army aviation operationsdemands for Army aviation support. Factors as they differ from normal operations and in theconsidered in support of tactical operations are application of special equipment and training.

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    3-28. Selection of Landing Sites

    a. Airfields.

    (1) During winter months the terrain offersmany landing fields for aircraft equipped withskis. Preparation of forward landing areas re-quires little effort; however, construction of per-manent or deliberate areas is often impracticable.

    Frozen lakes make excellent landing sites for bothfixed and rotary wing aircraft. Except for useas a hasty airfield, packing or removal of snowmay be necessary before lake surfaces are usable.Parking ramps should be cleared of snow andpaths provided for movement of heaters and aux-iliary power units if extended usage is anticipat-ed. A ground reconnaissance should be performedto insure uniform ice thickness and absence ofobstructions. Many lakes are subject to overflowfrom nearby streams, creating a mushy layerwhich can only be detected by means of groundreconnaissance. Aircraft equipped with floats can

    use lakes and streams for landing areas duringsummer months. Preparation of even temporaryforward landing areas during summer monthsmay require extensive engineer effort.

    (2) In a helicopter landing on either a floe orfrozen lake surface, the helicopter pilot shouldstart shutdown procedures only after he is surethat his landing surface is solid.

    (3) Determining the slope of potential land-ing sites in mountainous terrain is particularlydifficult due to illusions projected by adjacent con-tours. In addition, depth perception is impaired in

    snow covered mountain areas. Circling or flyingalongside the site will aid in overcoming theseproblems. Small trees, branches, bushes, or othermaterial dropped from aircraft can provide visualreferences.

    b. Helipads.

    (1) Selection factors such as size, approachesand exits, takeoff and landing direction, and secu-rity are the same as for normal operations.

    (2) Helicopter landing sites can be hastilyprepared in winter by packing the snow withtroops on skis or snowshoes or with tracked vehi-

    cles if available. Helipads should be marked by anobject that contrasts with the snow to provide areference for depth perception. The panel markershould not be used for this purpose, since itcannot be adequately secured to the snow coveredsurface.

    (3) In mountainous terrain, it is often nec-essary to prepare landing sites by pioneer meth-ods.

    (4) Helicopter operations in muskeg anddeep snow are hazardous because the basic designof landing gear offers no flotation.

    (5) Wheel-through-skis or skid pads shouldbe made available for northern operations duringall seasons. Utility helicopters equipped with skisor skid mounted pads do not provide sufficientflotation in deep powder snow and the helicoptercan settle deep enough to cause the tail rotor tostrike the snow.

    3-29. Weather Hazards

    a. General.

    (1) Flying conditions in northern areas nor-mally are good, when an entire year is considered.The cold temperatures greatly affect groundmaintenance, but rarely interfere with an aircraftat flight altitude.

    (2) Over the Arctic Ocean and along the

    flying weather usually prevails throughout theyear. Considering ceiling and visibility, the sum-mer months provide the best flying weather. Thisis true, although the number of cloudy days dur-ing the summer will exceed the number of cloudydays during the winter. Frontal activity duringthe summer is weak and will very seldom causesevere turbulence, icing, or strong winds. Thun-derstorms that develop during the summermonths can usually be circumnavigated and donot greatly interfere with operations. High windsfrequently limit flight operations in some areas.

    b. Visibility.

    (1) Northern weather conditions which fre-quently render flight impossible aresnow,clouds, fog, heavy rain, and whiteout.

    (2) Over the Arctic Ocean and along thecoastal areas, the main hazards to aircraft opera-tions are: blowing snow and strong surface windsduring the autumn and winter, and fog during thesummer. Blowing snow is a hazard in all opera-tions, but especially hazardous in hovering opera-tions. For this reason, hovering should be kept toa minimum. This restriction to visibility may bedeceptive to the inexperienced pilot because the

    shallowness of the layer of blowing snow usuallypermits good vertical visibility at the same timethat the horizontal visibility is very poor withinthe layer. It can be minimized by disturbing thesurface and allowing it to refreeze or consolidate.After consolidation the snow will crust and forma hard surface.

    (3) The major restriction to aircraft opera-

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    accurate identification extremely difficult. Pilotsmust exercise caution to insure proper orientationat all times.

    3-33. Maintenance

    a. The problems of increased maintenance stemdirectly from the low temperatures. Special pre-cautions and equipment are necessary to insureefficient operation of the aircraft. Operation ofaircraft at temperatures below 50F should notbe attempted except in emergencies, unless theaircraft, with appropriate winterization kit, andauxiliary systems have proven reliable at lowertemperatures.

    b. Reciprocating engines should not be startedat temperatures of 10

    0

    F, and below, without theuse of an electrical power unit for assistance instarting. A source of external heat for applicationagainst engine accessory case, carburetor induc-tion system, oil pump, and battery will insure eas-

    ier starting. The standard portable combustiontype heater, incorporating a blower and flexiblehoses for application of heat to localized areas,may be used for preheating aircraft componentsand systems before starting. In addition to pre-heating engines for starting, these units may alsobe employed to heat specific portions of the air-craft so that maintenance personnel can workwithout gloves. When temperatures remain belowfreezing, aircraft batteries not in use should beremoved and stored in a warm place.

    c. Thickening of oils at low temperatures pre-

    sents problems in operation and starting. An aidin extreme cold is the installation of standardwinterization equipment which includes baffles onoil coolers and engine cowl baffles to maintainproper temperatures. Oil dilution units may alsobe installed, although it is normally satisfactoryto drain the oil from engines at the end of thedays operations and to heat it prior to replacingit in the engine.

    d. So far as is possible, wheels should be kepton dry surfaces to prevent them from freezing tothe ground.

    e. Mooring of aircraft is made relatively simplein regions of extreme cold by the expedient of

    placing one end of a rope on the ground, coveringit with snow, melting the snow and allowing it tofreeze, then mooring the aircraft.

    f. Maintenance time factors may be multipliedby five in areas of extreme cold. Aircraft mechan-ics are greatly hampered by the heavy winterclothing and gloves. Installation of auxiliary

    equipment such as winter cowls, oil dilution sys-tems, personnel heaters, and covers also adds atime factor to normal maintenance operations.Maintenance units usually require additional per-sonnel in the airframe sections.

    g. Shelter must be provided for personnel per-forming maintenance. In the absence of mainte-nance tents, personnel parachutes placed over theequipment is a satisfactory improvised method.

    h. Operation of aircraft, particularly helicop-ters with their inherent vibrations, in tempera-tures below 35

    o

    F. results in a marked increase

    in metal fatigue. All metals become increasinglybrittle as the temperature decreases. This will beevidenced by an increase in the number of skincracks and popped rivets in stress areas. Carefulattention must be devoted to these areas in allstages of maintenance operations.

    3-34. Armament and Ammunition Handling

    The special care that is required to handle infan-try (para 3-4 and 3-5); armor (para 3-16); andartillery (para 3-24), ammunition and equipmentalso applies to attack helicopter systems and am-

    munition.

    3-35. Survival

    a. Training. A respect for the northern environ-ment should be engendered in all personnel. Per-sonnel should attend a survival course in living inthe field. This course covers construction of shel-ters, signals, wearing of clothing, and living offthe land.

    b. Equipment. Proper clothing is necessary forall personnel. Aircraft survival kits must be car-ried on all flights and passengers should be

    briefed on the contents of the kits before takingoff. These kits are authorized in CTA 50-901.

    Section V. CHEMICAL OPERATIONS AND BIOLOGICAL DEFENSE

    3-36. General the same as for temperate climates. The applica-tion of these principles to operations in northern

    The principles for employment of chemical latitudes or at low temperatures (below 320

    F.)agents, and CBR defense in northern latitudes are must be based upon a thorough understanding of

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    frost must be kept clear of the inlet valves. Assoon as possible after removing the mask, itshould be dried out in a warming shelter to insurethat it will be functional if required again in thenear future. Frostbite of the face may occur ifhead harnesses are adjusted too tightly.

    (2) Freezing and thawing does not affect thetherapeutic value of atropine; however, atropineinjectors must be protected from freezing to pre-vent damage from freezing rupture and to insureproper functioning.

    (3) Reagents in the chernical agent detectorkits must be protected from freezing. This can beaccomplished by carrying the kits underneathouter clothing. Although the validity of tests arenot affected by extremes of temperature, sometest may require longer periods of time for ap-proximate color changes under cold temperatureconditions. In extreme cold, the vapor concentra-tions above chemical contamination may be low

    enough to escape detection. The detection of theseagents may be facilitated by warming a smallsample of the contaminated material or by con-centrating the vapor beneath an inverted box orother suitable substitute and sampling from asmall hole in the container.

    (4) Water, the most common ingredient indecontamination operations, is useless if tempera-tures are much below 32

    0

    F. Certain organic sol-

    vents maybe used for limited decontamination ofessential equipment such as weapons, vehicledoors, and loading ramps, etc. The M13 decontam-inating and reimpregnating kit, individual, willmost probably not be affected by cold.

    (5) The multilayer clothing normally worn infreezing weather offers fairly good protectionagainst skin absorption of chemical agents and

    almost complete protection against these agentswhen frozen. However, there is a great danger topersonnel wearing contaminated clothing in aheated shelter. The heat will volatilize the chemi-cal agents and can thus produce casualties. Addi-tional clothing should be available for changingprior to entering heated shelters and separatetents or storm entrances should be provided forpersonnel to change clothing after they have beenexposed to contamination.

    3-38. Defense Against EnemyBiological Operations

    The principles for defense against biologicalagent attack in cold climates are identical to thosefor temperate climates; however, it will be moredifficult to assure the requirement for food, water,rest, and cleanliness in cold weather. Troops suf-fering from dehydration, or from lack of nourish-ment or rest, will be particularly vulnerable tobiological attack.

    Section VI. FLAME AND SMOKE OPERATIONS

    3-39. Flame Operationsa. Flame operations can be utilized to advan-tage in both offensive and defensive operations inthe northern latitudes. The standard portable andmechanized flame throwers have the same limita-tions as other mechanical type weapons contain-ing moving parts and rubber components whenoperated at low temperatures. Both weapons mustbe winterized as prescribed in TM 3-1040-204-14,TM 3-1040-206-10, TM 3-1040-209-12, and TM3-1040-211-12, before they will perform satisfac-torily. In addition to winterizing the weapons,special procedures must be followed in preparing

    thickened fuels used by these weapons to insurethat the fuels will gel. These procedures involveeither heating the fuel ingredients or, if this isimpractical, using a chemical additive called apeptizer. Thickened fuels should not be stored forextended periods of time, since they tend to dete-riorate after 48 hours and may not work satisfac-torily. For details pertaining to flame weapons,munitions and equipment see FM 20-33.

    3-14

    b. At low temperatures, the ignition of flamethrower fuels may not occur readily. To insureignition, two or more charges from the ignitioncylinder should be ignited before firing a burst,SOP for the employment of flame weapons shouldprovide that sample batches of thickened fuels beprepared and the weapons be test-fired under con-ditions approximating those expected to be en-countered at the time of employment (TM 3-366,TM 3-1040-204-14, TM 3-1040-206-10, TM3-1040-209-12 and TM 3-1040-211-12).

    c. F1ame expedients (FM 20-33) involving theuse of thickened and unthickened fuels do not suf-

    fer from the same limitations as do mechanicalflame throwers. These weapons, if properly fabri-cated and emplaced, will perform satisfactorilyunder all conditions of temperature. Since igni-tion at low temperatures is more difficult, addi-tional ignition charges in the form of incendiariesshould be incorporated in flame expedients.

    d. Low temperatures have little or no effect on

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    field are particularly vulnerable to all of the ef-fects produced by a nuclear detonation because oftheir inability to dig foxholes and undergroundfortifications. Shelters and fortifications con-structed from snow and ice provide some protec-tion and, wherever possible, should be constructedto take maximum advantage of the additional pro-tection provided by natural terrain features. Dur-

    ing the winter months, the trunks and limbs oftrees will be frozen and become very brittle andwill reconverted into many projectiles moving athigh speed. Unprotected personnel in blast areaswill suffer many punctures and lacerations fromthese projectiles. In mountainous terrain withheavy snow covering, units should be aware ofthe possibility of avalanches resulting from theblast effects of a nuclear weapon. The snow cov-ered terrain and the atmosphere of some regionsincrease the reflectivity and improve the trans-mission qualities of thermal radiation; however,heavy, larger, lightly colored type clothing fur-

    nishes virtually complete protection againstthermal radiation, outside the radius at whichother effects will govern.

    b. Tents which provide necessary warmth forliving will not provide protection from radioactivefallout. Maximum use, consistent with the tacticalmission, must be made of natural terrain featuresto provide protection against nuclear radiation.Snow and ice, although not as effective as earth in

    reducing radiation hazards, are readily availableand can be used to provide shielding against ra-diation effects. Loose snow falling on a contami-nated area has a half-thickness of about 60 cm(24); that is, 6O cm (24) of loose snow coveringthe contamination will reduce the dose rate toabout half the original value. Thirty centimeters(12) of hard packed snow will reduce the dose

    rate by about and may be of value for con-structing radiation shields over contaminatedareas or around shelters.

    c. Low temperatures will also make the decon-tamination of personnel who have been in radio-active areas more difficult. The requirement thatcontaminated personnel be provided with bathingfacilities and a change of clothing must often bemodified and field expedient methods utilized.Field methods consist of removal and vigorousshaking of all outer clothing, or the use of brushesimprovised from shrubbery for brushing the

    clothing. When in a contaminated area, personnelshould keep clothing completely buttoned in orderto minimize contact of radioactive materials withthe skin. Tracking of contaminated snow intoshelters and populated areas can be minimized iftrails and roads are scraped after fallout ceases.If practicable, the removal of the top layer ofcontaminated snow within an occupied area willmaterially reduce the radiation dose rate.

    Section VIII. ENGINEERS

    3-44. General

    Engineers in northern operations carry out theirnormal combat, combat support, and combat serv-ice support missions. Special aspects of combatservice support tasks are covered in TM 5-349and FM 31-70. Environmental factors increasethe volume and scope of engineer operations andthe difficulties attendant to execution of these op-erations. The scarcity of trails, roads, and air-fields increases the need for construction effort.At the same time, the effect of the extremes ofclimate increases the manpower and equipment

    effort required for both construction and mainte-nance. The numerous streams, swamps, and lakesnecessitate increased quantities of stream cross-ing equipment and correspondingly increased ef-fort for its installation and maintenance. Cross-country movement of large forces requires aug-mented engineer effort. The problems confrontedin construction of conventional engineer field

    works are magnified, as are the problems of in-stallation of field fortifications. While water po-tential is normally adequate, the difficulties ofsupplying potable water by conventional methodsare increased.

    3-45. Field Fortifications

    a. Troops must be capable of constructing fieldfortifications on snow and frozen ground usingmaterials available. This may include constructingobstacles with wire, mines, and timber under thespecial conditions of winter and by the icing of

    banks and the preparation of traps in the ice ofrivers and lakes.

    b. Excavation is difficult in frozen ground,therefore, hand tools are of little use. Explosivesare effective but large quantities are required.Charge calculations cannot be made directly fromdata in FM 5-25, because of variations in mois-ture content, soil types, and vegetation as well as

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    frost into any unstable subgrade, consolidatingthe subgrade. The snow removed from the road isscattered away from road ditches. Piling of snowor forming of snow banks along the road creates acondition favorable to the deposit of snowdrifts.Deep-rutted snow which is hardened by traffic orfreezing can be leveled with harrows, drags, grad-ers, dozers, or by packing loose snow into ruts.

    Road surfaces, culverts, bridge channels, andditches are maintained and kept clear to providemelted snow drainage. Maintenance of roadsmade by combat troops for tracked vehicles nor-mally consist of such tasks as straightening sharpcurves, filling holes, building turnouts, and drain-ing surface water. Frequently, winter traffic ef-fects on snow roads will result in a loose snow-soilmixture which cannot be compacted. If tempera-tures are sufficiently low, this condition can becorrected by adding water and restoring stabilityby freezing. In the more common case, tractioncan only be restored by removing the unstable

    material.

    3-47. Ice Routes

    a. General. In some areas, the best sites forwinter road routes will be found along frozen wa-terways. They have an advantage in that they arerelatively easy to prepare, requiring only snowremoval and possible strengthening of the ice inplaces, and the only slopes found on such routesare at the entrance and exit to the waterway.However, disadvantages are many: A sudden tem-perature rise can make the route unusable, manymen and much equipment must be stationed alongthe route to effect continuous maintenance andrepair, convoy speed is limited, and recovery oper-ations of vehicles which break through the icemay force traffic to seek alternate routes.

    b. Planning. Tactical plans should not be basedon ice routes and bridges unless there are no otheralternative solutions. The many variables con-nected with ice routes and bridges make tacticalplans based on ice bridges and routes risky atbest. If ice bridges are used, fixed bridging shouldbe installed as soon as possible to insure continu-

    ous use during warming and high traffic densityperiods.

    c. Reconnaissance. Road routes over and acrosslakes and streams are selected only after intensiveand detailed reconnaissance of ice conditions. Thisreconnaissance is concerned mainly with deter-mining the ability of the ice to support the heavi-est load which it must bear. The reconnaissance

    for a route over ice must be conducted by person-nel qualified to interpret ice characteristics to pre-vent men and equipment from being needlesslyendangered. The entire route over ice must bechecked as the ice can differ in many ways in arelatively short distance.

    d. Strength of Ice. The strength of ice varieswith its structure and temperature. A snow coveror a warm current will affect the ice temperatureand generally will produce a thinner and weakerice cover. Table 2 provides working capacity fig-ures for planning purposes.

    e. Expedient Crossing. An expedient for a tacti-cal crossing of skiers, snowshoes, and oversnowvehicles may be used when a detailed prior recon-naissance is impossible. Leading men of the trail-breaking party are roped together. The lead trailbreaker in a prone position drives an axe into theice at arms length; if the ice sounds solid hemoves forward 5 meters (5 yds ) and tests again.

    f. Ice Bridges. If the conditions are favorable,an ice bridge may be easily constructed. Construc-tion of an ice bridge requires pumps or someother means of flooding the ice, and freezing tem-peratures. Temperatures below 10

    0

    F. are desira-ble. If the ice is exposed to direct sunlight or thetemperature is above 25

    0

    F., flooding should bedone in the evening to take advantage of thecolder night temperatures. Time spent selecting agood site will be well repaid in reduced construc-tion and maintenance effort. It takes less effort toconduct an adequate reconnaissance of a crossing

    site than to extract a vehicle which has brokenthrough the ice. A site should be located which,within the tactical limitations, provides the bestcombination of shortest distance, gradual slopingembankments, and low turbulence. The natural iceshould be at least 10 cm (4) thick at the siteselected in order to support men and equipmentrequired to construct the ice bridge. A checkshould be made to insure that there is water flow-ing under the ice, and that there are no hotsprings present; otherwise, construction of thebridge would be impossible. For details of icebridge construction, see TM 5-349.

    3-48. Airfields

    a. The preparation of airfields for fixed wingaircraft depends upon the conditions encountered.In deep snow, the surface must be smoothed andpacked by the use of a drag or by driving vehiclesover it. With a small amount of pioneer work,hard wind-packed areas can be made usable for

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    and the mission of the force. During the planningstages, all these factors must receive detailedstudy to determine the proportion of engineers inthe task force, the type of equipment needed, andthe organization they require.

    c. Environmental characteristics of northernareas which complicate engineer tasks are

    (1) Permafrost.(2) Extreme and rapid temperature changes.(3) Wind, snow, and ice storms.(4) Flooding.(5) Alternate thawing and freezing.(6) Terrain such as mountainous, muskeg,

    or tundra regions.(7) Hot springs.

    d. Specific engineer tasks complicated by north-ern conditions are

    (1) Water supply.(2) Fire protection systems.

    (3) Road construction and maintenance.(4) Bridge construction and shore work.(5) Construction of appropriate defensive

    systems.(6) Mine and antimine warfare and reduc-

    tion of other obstacles.(7) Construction of airfields, airstrips, and

    helicopter landing sites.(8) Installation and maintenance of camou-

    flage and decoys.(9) Construction of storage and supply dis-

    tribution areas.(10) Construction of troop shelters and ad-

    ministrative facilities.e. In the north, as in any undeveloped area,

    much is required of the engineers to facilitate themovement of the command. Extreme cold adds tothe importance of efficient organization for engi-neer work. Parties forced to stand about idle inthe open rapidly become chilled and lose much oftheir efficiency. Tasks must be laid out, and equip-ment and materials should accompany work par-ties. Firefighting equipment and techniques differin extreme cold because of the problem of procur-ing and transporting water. Fire prevention mea-

    sures and inspection are of the utmost importanceand must receive constant attention. Water that isstored for firefighting purposes should havecalcium chloride added to keep it from freezing.The chief reliance is upon nonfreezing firefightingchemicals. It is unsafe to rely on the use of snowto extinguish fires because the snow is usuallytramped clown around structures within a campand is therefore unavailable in sufficient quanti-ties.

    (1) In the provision of shelters, it should beborne in mind that less fuel is required to provideadequate heat for one large space than if the samespace is divided between two or more structures.This is because of the reduced area of outer walls,in the former case, through which heat escapes.

    (2) Gasoline burning, portable tent heaters

    of the airduct type which rely on a small gasolinemotor to operate the blowers can be modified, ifelectric power is available, by replacing the gaso-line engine with an electric motor to make themmore reliable in operation and to be less of a firehazard.

    (3) In semipermanent camps, where gasolineor fuel oil stoves are employed, the usual 5-gallongasoline can should be replaced with tanks madefrom one or more 56-gallon drums set up onstands outside the tent or building, with fuelpiped inside to the stove. Frequent inspections for

    fuel leakage must be made and corrective actiontaken to eliminate all fire hazards.

    3-53. Water Supply

    a. The problem of supplying water in the northto units up to battalion size or reinforced brigadesis much greater than that of individual supply.For instance, melting snow and ice on stoves,burners, or open fires in sufficient quantities toprovide water for all needs of large units is im-practical because a large amount of fuel is neededto obtain a small amount of water. Seventeencubic inches of loose snow, when melted, yieldsonly 1 cubic inch of water. Melting of snow is notrecommended for supplying water in quantityexcept in an emergency. The chief sources ofwater supply for large units in the order of theirefficiency and economy are: drawing water fromunder river or lake ice, melting ice, melting snow,and well drilling (semipermanent and permanentcamps).

    b. When possible, water points on lakes andrivers are located on the leeward side where thereis generally clearer water, less snowdrifting, andmore shelter from the wind. Sites on a lake arelocated as far from the shore as possible, withineffective camouflage limitations. To cut holes inice at water points, ice augers, air tools, steam

    jets, or other such equipment prove most effective,holes can also be drilled through ice by the use ofhand augers, however, shaped charges are far su-perior to hand tools in preparing water holes inthick ice since hand tools are generally inefficientif ice is over 60 cm (24) thick. A point to note in

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