Eventually, Finland was able to roll back the Soviets’ tank advances with these drive-by ski bombings. And on Dec. 6, Stalin’s army mounted a large-scale infantry invasion near the Taipale River. The Soviets, having a huge numbers advantage, plowed through the snow towards the enemy.

But the Finnish ski troopers, again utilizing their knowledge of the white and wooded landscape, expertly positioned automatic weapons that mowed down wave upon wave of advancing Soviet soldiers.

After days of slaughter, enough dead riflemen had piled up in the snowbanks that the oncoming lines of Soviets were able to take cover behind the frozen bodies. The sub-zero temperatures hardened the corpses enough to stop the Finnish machine gun rounds.

On Dec. 17, having taken heavy losses, the Soviets shifted their focus to a different area of the Finnish front known as Summa and Lahde. The Soviets used flamethrower tanks to scorch the Finnish trenches while the Finnish army fought back fiercely. It’s been said that two machine gunners fired 40,000 rounds between them.

In the evenings, the Finnish ski troops counterattacked. By Dec. 21, Stalin’s birthday, seven Soviet infantry divisions had been wiped out along with 250 T-28 tanks.

A bitter winter fell. Temperatures plunged to negative 40 degrees Fahrenheit. It was so cold that when a soldier was hit by a bullet and his circulation slowed, his body would freeze almost instantaneously, immortalizing his agonized posture.

Later, the Soviets entered Finland from the eastern border and walked narrow logging trails in the woods with more than 30,000 troops. Included in this line were aerosani—propeller-driven snowmobiles with mounted machine guns. These snow-skimmers had been developed for delivering mail and medical aid in Siberia.

The Finnish ski troops approached the lines from the front and back and knocked out the lead and trailing vehicles, causing the middle units to become stuck. Swiftly, the Finns jumped out of the forest and further split the Soviet columns with mortars and grenades. In this way, the Finns decimated the long Soviet columns and took 1,500 prisoners.

In January both sides recessed and regrouped as the cold became unbearable. When the Soviets returned in February they launched an all-out assault, sending 45 divisions—a total of 750,000 troops—into the forests of the Karelian Isthmus.

Two thousand artillery shells slammed into the Finnish front line. There were simply too many Red Army troops for the Finnish ski troops to dexterously out-maneuver their foes—and as a result Finland’s army could not hold.

The Finns sent in their reserves. The fighting raged on, with Stalin’s army slowly pushing back Finland’s infantry. By March 12, the Finnish ski troops were almost out of ammunition. But the next day, March 13th, 1940, Helsinki and Moscow signed an armistice. Having largely held back the USSR, Finland sacrificed some territory for an end to the fighting,

All told, it is believed that the Finnish army killed more 200,000 Soviet soldiers for a loss of fewer than 50,000 its own.

When the snow finally melted that spring, the corpses of thousands of Soviet soldiers were unearthed in the Finnish woods, each body still contorted as in its final moments of life.