Boots on the Ice: Physiology when Operating in Extreme Cold

Why the Arctic?

The Arctic is rapidly shifting from inaccessible, frozen desolation to the forefront of U.S. security policy. Faced with increased activity from near-peer competitors (especially Russia and China), increasingly open sea lanes, and increasingly accessible energy and mineral resources in a thawing High North, the Department of War considers the Arctic theater a critical component of U.S. homeland defense and an area of strategic competition.

Anywhere in the world, strategic success requires boots on the ground- or, in the Arctic, boots on the ice. This creates unique challenges, since humans are, physiologically, desert animals. Military personnel in places like the Alaskan interior routinely contend with temperatures averaging below -10^oF, with extremes as low as -80^oF.

In this article, we explore why military competition in the Arctic is increasingly contested and how human thermal limitations challenge operating in this extreme environment. We’ll consider a battle during the Winter War of 1939-1940 to highlight the importance of maintaining thermoregulation and preparing for the operating environment in military Arctic and sub-arctic combat.

Man in the cold

Modern human ancestors lived in hot environments. Today, humans retain adaptations selected for efficient heat loss, not heat retention. These adaptations greatly benefitted early humans, who travelled long distances to forage in relative safety during the hottest parts of the day when predators (which lack efficient heat dissipation methods) were less active. However, these evolutionary adaptations challenged our early ancestors when they left Africa for colder, northern climates.

The clearest demonstration that humans evolved to dissipate, rather than retain, body heat is found by comparing our physiological ability to dissipate heat with our ability to generate it. If humans evolved to live in cold climates, keeping warm would be more of a concern that cooling off. This is clearly not the case:

Warming values as described by Dr Hein Daanen. Cooling values assuming 3 L/hr sweat rate with complete sweat evaporation. Individual values will vary, but those shown are good, order-of-magnitude approximations for healthy, acclimatized young adults.

The comparison between our ability to cool and to generate heat is not even close. To prevent body core temperature dropping in cold environments, humans can generate only about 315 watts of thermal power,[1] mostly through violent shivering. Even this modest amount comes at the extreme energy cost of burning about 300 extra calories per hour (and assumes your muscles can sustain the effort required for such intense shivering). It’s also nearly impossible to work while violently shivering, especially if such work requires skillful coordination like aiming a weapon or operating equipment!

This physiologically generated additional warming is nearly ten times less than the amount of cooling power (~2,000 watts) we generate at our maximum sweat rates. Sweating also requires far less energy. Evolution has clearly worked to provide us strong protection against overheating in hot environments while leaving us essentially helpless to generate excess body heat in cold environments.

From Biology to Technology

Although we can’t rely on physiology alone to live in cold environments, humans have clearly found a way to thrive well outside the (hot) biological niche we evolved in. The secret is uniquely human- our ability to develop social and technological solutions for living and working in the cold.

The most obvious technological adaptation to the cold is clothing. Your winter Patagonia jacket has a long lineage; archaeologist believe humans first started wearing clothing more than 100,000 years ago. Today, military personnel in Arctic environments receive seven distinct layers of thermal clothing in addition to specialized sleeping bags, gloves, and boots (described in this Qore Performance article). There is even a research department (Thermal and Mountain Medicine) within the Army’s Research Institute for Environmental Medicine that specializes in developing and fielding the latest gear for warfighters operating in extremely cold environments.

Cultural adaptations also allow us to thrive in extreme cold. In a military context, this includes the operating procedures and standards practiced by units in the Arctic. There is even a military medical manual dedicated to cold stress management, cold injury prevention, and tips for operating in extreme cold conditions.

The Simmering Threat in the Cold North

In an unforgiving environment like the Arctic, preparation and proper equipment are vital. In a winter conflict, knowing the effects of the extreme cold environment will be just as important as knowing the enemy. The Arctic is an extreme and dynamic region rapidly becoming a new theater of great power competition. As the high north becomes increasing contested, the U.S. and its allies are increasingly aware of the need to address novel challenges in a region long left neglected.

The Department of War began seriously preparing for Arctic competition with the release of a Arctic Strategy in 2024. This document highlights the growing cooperation between Russia and China (the later calls itself a “near-arctic State” despite being 900 miles away from the Arctic circle). Russia, increasingly relying on economic and military ties with China to pursue it’s war in Ukraine, has begun shipping energy along the Northern Sea Route to China using it’s “shadow fleet”, while China is investing in (potentially dual use) port and logistical infrastructure in the Russian Arctic.

To counter the rising threat Russia and China, the U.S. Arctic Strategy calls for a Joint Force capable of conducting mission-essential tasks “at extreme temperatures routinely reaching -50^oF or below”. It stresses the need for all services to train Arctic capable forces in cold weather operations like over-snow mobility, medical care, and survival. While undoubtedly true, putting those goals into practice is easier said than done. A 2023 RAND report highlights “humans who are unprepared for the physical, mental, and emotional challenges of the Arctic [have] a direct implication for the United States’ ability to maintain a presence in the region. Humans cannot survive in this region without proper training, experience, and equipment.”

The Cost of Being Unprepared

There is no better example of the cost for being unprepared for Arctic combat than the Winter War of 1939.[2] With many parallels to today’s war in Ukraine, this conflict saw a massive but poorly prepared Soviet army attempt a land grab and regime change in Finland, only to find itself fought to a standstill by the smaller but motivated Finnish defender.

The Battle of Suomussalmi is a textbook case of how extreme cold can be a combat multiplier for a prepared force, or a deadly foe for those unprepared. Located in central Finland, the municipality had few improved roads and, at the start of the month-long battle in December 1939, plenty of snow. As many as 55,000 Soviets, recently victorious in Poland and well equipped with tanks, armored vehicles, and other instruments of (then) modern war, faced a Finnish reserve force one-fifth their size. The result was an unqualified defeat of the invading Soviet columns.

To defeat the Soviets, the Finnish defenders skillfully employed their knowledge of the local terrain and weather. Daily temperatures hovered just above 0^oF, with overnight lows dropping below -20^oF (and, in some accounts, much colder); brutal conditions for sure, but not unusual to the rugged backwoodsmen that comprised much of the defending Finnish force. These Finns knew how to operate in this extreme cold, remaining mobile on skis while the Soviets remained largely stuck along sparse, narrow roads.

Striking strategically at weak points along the Soviet column, the Finns cut the invading divisions into sections, isolating smaller pockets of Soviets in mottis, named after sections of cut logs many of the Finnish loggers-turned-soldiers chopped for firewood. The Finns didn’t have to kill every Soviet soldier; left isolated and immobile, the extreme cold performed that task.

Perhaps nothing better demonstrates the Finnish understanding of cold weather operations than the targeting of Russian field kitchens. Easily observed by their smoke, 50 or so field kitchens were the only source of hot food for the Soviets. Destroying these kitchens deprived the Soviet invaders of morale and physical sustenance, both vital to operations in extreme conditions (recall above, our limited ability to generate additional body heat comes from burning calories). In fact, one of the two Soviet commanders, General Vinogradov, was executed by Soviet political police for (among other failures), “the loss of 55 field kitchens to the enemy” after fleeing the battle in a tank. The body of the second Soviet commander was never found.

The Soviets who didn’t manage to flee faced a similar fate. With maneuver impossible, Soviets in isolated pockets faced a losing dilemma- huddle around bonfires and become easy targets for Finnish snipers, or freeze to death in the cold. By the end of the battle, the Soviets suffered more than 27,000 casualties, many frozen stiff where they fell in the Finnish woods.

The Battle of Suomussalmi. Blue arrows indicate Finnish attacks against the (red) Soviet column. Gaps in the Soviet column show where Finnish forces, able to maneuver in extreme cold conditions, isolated sections of the larger but extended Soviet force. Original source: United States Military Academy; obtained from wikicommons.

Lessons from Suomussalmi

Although it is easy to draw lessons of what not to do during cold weather combat from the Soviet defeat, equally important are the lessons the Finnish defenders teach us about operating in Arctic conditions. The Finns knew, and the Soviets quickly learned, that cold kills as well as any bullet. The Finns understood the importance of keeping troops warm in the extreme cold. Cold leads to exhaustion, poor thinking, frostbite, and the collapse of morale.

Finnish commanders established warming shelters for soldiers, keeping troops comfortable right up to moment they deployed for attack. Similarly, during and after a raid, tents would often quickly be established to rewarm the attacking force and serve as aid stations. Soldiers were continuously rotated into these warm shelters for a hot meal, warm cup of hot coffee, and a few hours’ sleep; every two or three days, Finnish soldiers could even look forward to a brief trip to a frontline sauna. In contrast, the Soviets remained out in the cold for the entire battle, unable even to provide warm shelter for casualties.

Even in today’s high-end, technologically saturated battlefield, we neglect thermoregulation on a frozen battlefield at our own peril. Qore Performance provides the next generation of tools for fighting in extreme cold. These can be filled with hot water to assist thermoregulation when the temperature drops. Like Finnish frontline warming efforts in the winter of 1939-1940, Qore Performance ICEPLATE® and ICEFLASK™ reduce physiological effort in extreme cold, boost performance, increase endurance, and keeping us mentally alert.