Weaponizing Winter: Operating in Cold Environments
Cold weather adaptation can be the difference between comfort and misery during an outdoor winter work shift, hike, or festival. Cold adaptation (or the lack of) can also have more serious consequences than discomfort. Throughout history, poor winter preparation has decimated unprepared armies. “General Winter” twice helped save Russia from defeat, first when Napolean’s invasion suffered in the cold (by some accounts, the French general lost 40,000 dead to exposure in a single four-day period during his retreat), then again when German soldiers suffered some 100,000 cases of frostbite on the Eastern front during World War 2. But Russian soldiers haven’t aways held an advantage in the cold. Finland avoided forcible assimilation into the Soviet Union due to poor Russian preparation and Finnish fighting skill in the extreme cold during the “Winter War” of 1939-1940.
As with any operation, in cold weather, “luck” favors the prepared. With global competition among rivals (e.g., Russia) increasing and the Arctic thawing, competition in the High North is escalating. In response, the U.S. Army is reemphasizing training in extremely cold environments. The 11th Airborne Division (“Arctic Angels”), reconstituted in 2022 from elements stationed in Alaska, includes defeating “any adversary in extreme cold weather” in its mission statement. The 11th Airborne is just the most recent American unit to equip and train for cold weather combat. The 10th Mountain Division, formed during World War 2, trained on ski slopes in Colorado for combat in the Italian Alps, and toward the end of World War 1 the American Expeditionary Force, dubbed the “Polar Bears”, fought Bolshevik forces in the Russian Arctic.
This article highlights adaptations and preparations for military operations in extremely cold environments. Drawn from techniques employed by U.S. Army units and the author’s experience stationed at Ft. Wainwright, Alaska, these lessons can be applied to anyone operating, working, or recreating in cold weather.
Fundamentals of Operating in the Cold
Four factors contribute to cold stress: temperature, wind speed, dampness, and water. Since most of us likely won’t ever experience a cold-water immersion scenario, we’ll ignore “water” to focus on the first three.
Temperature’s contribution to cold stress is intuitive; if the environment is cold enough to draw body heat away faster than metabolic heat is generated, core temperature drops, physiological responses to cold begin, and hypothermia becomes likely. “Thermoneutrality” is the environmental state where core temperature can be maintained without requiring additional metabolic effort for cooling or warming. The thermoneutral point for a naked human is around 84oF. With light clothing to trap some body heat, this temperature drops to about 70oC. Below the thermoneutral point, energy must be expended to maintain a stable core temperature around 98.6oF.
Models estimating survival time for people without adequate clothing predict death after about 15 hours at -4oF and 8.6 hours at -22oF. By assuming death occurs at a core temperature of 86oF, these estimated times may be optimistic; extreme discomfort and hypothermia (a core temperature below 95oF) happen much more quickly.
Figure: Pre-hypothermic temperatures in various areas of the body during cold exposure. Note the body core remains at 98.6oF (37oC) while extremities cool in an attempt to keep vital organs warm (see our post on Thermal Physiology in the cold). If the body core region drops below 95oF, humans become hypothermic. Figure adapted from U.S. Army TB MED 508, Prevention and Management of Cold-Weather Injuries.
Wind speed increases the risk of cold stress by drawing additional heat from the body. Wind speeds are used to estimate the wind chill temperature. Wind chill temperature is the hypothetical temperature in still air that would create the same heat loss rate in a person as the combination of actual wind speed and temperature. Increasing winds correspond to increasing danger of hypothermia to about 40 miles per hour (after 40-mph, higher wind speeds don’t have much additional effect). The Army manual for cold weather injuries (TB MED 508) lists wind as a cold weather hazard if 5-mph or greater. The table below shows the wind chill temperature chart used by Army training units. Under calm conditions, “increasing danger” for freezing exposed flesh in properly clothed soldiers begins at -30oF, while a 20-mph wind speed creates dangerous conditions much sooner- at temperatures as warm as 10oF.
Table: Wind chill temperature chart from Army Regulation 350-29, Prevention of Heat and Cold Casualties.
Hypothermia is possible even above 40oF if a person is wet from rain or sweat; the Wilderness Medical Society notes cold and wet environments pose the greatest risk for hypothermia. In one experimentexploring the combined effect of cold and wet, 18 men were asked to walk for 5 hours at 41oF, with simulated rain during the last 4 hours. Eleven could not complete the test and two developed hypothermia. Staying dry is clearly critical for avoiding hypothermia. In Cold, a recollection of a lifetime exploring polar regions, Sir Ranulph Fiennes frequently relied on metabolic heat generated by hauling heavy sleds to keep warm on polar expeditions. During even brief halts, he recalls sweat collected on his cloths quickly freezing, forcing him to immediately set up shelter or resume intense physical activity.
The Right Equipment
Having the right equipment in cold environments is the difference between mission success and becoming a cold weather casualty. To operate in extreme environments, U.S. Military issues the Extreme Cold Weather Clothing System (ECWCS). ECWCS is designed to be worn in three-layer combinations that can be adjusted based on mission and environmental conditions. There is nothing inherently unique about the ECWCS system, and protection from cold injuries can be obtained from similar layering with civilian clothing.
The first, inner layer (known as the ECWCS “level I”) is a base layer designed to wick away moisture against the skin. This base layer is similar to what outdoor enthusiasts know of as “long johns” or light thermal underwear. A critical feature of this layer is that it is light- while it traps some body heat, it is intended to keep the skin surface dry, not retain large amounts of heat. I’ve found a good base layer and light outer garment often sufficient to stay warm if working outdoors, such as during snowshoe hikes in the hills north of Fairbanks, Alaska.
The second layer is an insulation layer. While this layer is also moisture wicking, its primary purpose is to trap air against the body; this trapped air warms up from metabolic heat. The ECWCS system has two different layers, a “level II” shirt and drawers and a heavier “level III” fleece top. The level III is typically worn in extremely cold environments when not moving, while the less insulating level II can be worn when patrolling or otherwise engaged in activities that generate large amounts of metabolic heat. A common practice in Arctic units is to craft a pair of underwear by cutting a pair of level II pants into boxer or shorts. This keeps a sensitive area warmer while not covering the entire leg, which when on the move may be too much insulation and lead to overheating.
The third layer is an outer shell designed for protection against the elements. The lightest outer shell in the ECWCS system is the “level IV” wind jacket. In Arctic conditions, the “level V” soft shell jacket and pants are most common. Stretchy, breathable, and (if worn with appropriate base and insulating layers), very warm, the level V combination is the typical outer garment worn during military operations in the cold. For extreme cold conditions, or when movement is limited, the “level VII” parka and trousers are also worn. Similar to a heavy down parka, the level VII shell is so warm that it is almost never needed when patrolling, since it traps metabolic heat so efficiently that the wearer would risk overheat even in extremely cold conditions.
(I skipped “level VI”, a waterproof jacket and pants. In my experience at Ft Wainwright, Alaska (about 100 miles south of the Arctic Circle), I never had much use for this layer. Temperatures were so cold- usually far below zero- and the ECWCS system so well designed that snow and ice on the outer layer could be brushed off before it melted. If temperatures were more often right around freezing, this layer would have been used more frequently).
Dressed for extremes: C-O-L-D.
The acronym COLD is helpful for dressing in cold environments.
C: for keeping it Clean. Clothing must be kept free from dirt and oils. Anything that reduces the garments’ ability to wick moisture or trap air leads to reduced thermal insulation.
O: avoid Overdressing. The rule for the beginning of any cold weather mission to start cool. When first stepping off, you should be a bit chilled, ready to begin movement and warm up. Anyone comfortable outside before the mission begins is overdressed and likely to overheat once they start a working effort and generating significant metabolic heat.
L: wear it Loose and in Layers. To avoid overheating, wear layers and adjust according to activity. During periods of heavy effort, such as movement on snowshoes or pulling a sled, the body warms by burning calories. Fewer, lighter layers should be worn to prevent overheating. When stopped, metabolic heat production drops, and additional layers should be added. The goal is to remain in a “goldilocks zone” where the combination of layers and metabolic heat keeps you warm enough to work but cool enough to prevent sweat or overheating.
D: keep it Dry. Sweating is dangerous in cold environments. Layering must be sufficient to prevent core temperature from dropping but not so much that excess heat is retained, causing an individual to sweat. Snow and ice must be brushed off before it can melt, and inner layers of clothing must never get wet from rain or melt water. Once wet, it is difficult to dry out in cold environments.
The Right Training
The right knowledge is as important as the right equipment for operations in the Arctic. Due to frequent troop rotations, the Army trains thousands of soldiers each year who arrive in Alaska without Arctic experience. Often these new soldiers are straight out of basic training and may never have experienced temperatures cooler than a January night in Alabama or Florida!
To ensure new arrivals can not only survive but also fight and win in extreme cold, Alaskan units conduct cold weather certification classes and exercises each Fall as temperatures dip. To ensure leaders are trained, the 11th Airborne Division also runs the Northern Warfare Training Center (NTWC) in the Alaska Range mountains.
Three winter classes are taught at NTWC. The “easiest” is the Cold Weather Orientation Course (CWOC). CWOC consists of five days of field practice, including an overnight in an improvised, unheated snow-and-log shelter that students construct. Key to staying warm in this shelter (or at least not freezing) is trapping heat generated by yourself and your buddy in the smallest area possible and blocking the exit (from which warmer air could escape) tightly with a ruck sack. I count one particular night spent in the confined, coffin-like shelter, wrapped in a heavy sleeping bag under hundreds of pounds of hastily constructed snow and log, as among the most uncomfortable and mentally difficult of my life.
The Cold Weather Leaders Course (CWLC) is the second Arctic survival course taught at NWTC. In addition to basic survival practices, this two-week course includes rehearsing Arctic patrolling on skis and snowshoes along with risk management and cold injury medical treatment. Squad leaders and platoon sergeants graduating this course carry their new skills back to their units, ensuring lessons in Arctic warfare are continuously refreshed and taught to the newest rotation of soldiers.
The third class taught at NWTC is the Isolation Survival in Cold Regions Course (ISCRC). Designed for personnel at high risk of isolation in the Arctic, such as downed pilot or scouts, this is the most extreme of the three winter courses. Students not only learn basic cold weather survival and movement techniques but also how to trap wild game and operate while isolated in temperatures that can drop below -40oF.
Image: Cold Weather Indoctrination Training at the Northern Warfare Training Center. The uniform in this picture appears to be level I and level V; no intermediate layer II is worn, likely because of the large amount of metabolic heat generated by the effort required to move a loaded ruck sack over the snow. Photo credit: SPC Samantha Magers/Defense Visual Information Distribution System.
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About the author: Erik is a doctoral candidate at Duke University where he conducts research on the challenges rising temperatures pose for military training. An Army veteran, Erik has served in a variety of extreme climates ranging from deserts in the U.S. Southwest and Middle East (120oF) to Arctic conditions in central Alaska (-42oF).