On November 30, 1939, nearly half a million Soviet troops stormed into Finland, beginning what would become known as the Winter War. The surprise attack came after the Kremlin, fearing a possible Nazi offensive through Finland, had insistently called for a land swap that would have pushed the Finnish border away from Leningrad (now St. Petersburg). Wary of Soviet intentions, Finland’s government refused. Soviet planners assumed an easy victory in time for Josef Stalin's 60th birthday on December 21. It was not to be. Although the Red Army would eventually win the war, the defeat of the country of just 3.7 million people came only months later -- and at a terrible cost.

These pictures are some of the approximately 7,000 images of the Winter War from the Finnish Defense Forces archive that were digitized and released to the public in 2013.

Amid an international outcry over the unannounced attack on Finland, Soviet Foreign Minister Vyacheslav Molotov claimed on the radio that planes were dropping food supplies -- rather than bombs -- to hungry Finns.

Showing their dark sense of humor, the fighters named the firebombs after the Soviet foreign minister as a "drink to go with the food" that Molotov had claimed to be dropping on Finland. Thus giving birth to an oft-used weapon in conflicts through the decades since.

Much of the weaponry used by the Finns was captured from Soviet forces.

The invading Red Army troops initially wore dark uniforms, making them easy targets for Finnish sharpshooters.

Professional farmer and hunter Simo Hayha reportedly killed more than 500 Soviet soldiers during the Winter War, before he was shot in the face and badly wounded by a Soviet sharpshooter. Late in life, when asked if he regretted killing so many young men, he responded, "I only did what I was told to do, as well as I could." Hayha died in 2002 and was buried under a tombstone reading "Home -- Religion -- Fatherland."

In contrast, Soviet armor could be heard from kilometers away, and was largely reliant on the few roads that cut through the Finnish wilderness.

As columns of Soviet troops and vehicles filed along forest roads, Finnish ski troops were able to stealthily move into position and destroy vehicles at the front and rear. With the road blocked the Finns could then encircle and destroy the trapped Red Army columns.

In the years leading up to the Soviet invasion of Finland, the purge of the Soviet military during Stalin's Great Terror left the army's command structure in disarray.

In January 1940, Britain’s Winston Churchill said of the ongoing war, "Finland shows what free men can do.... Everyone can see how communism rots the soul of a nation; how it makes it abject and hungry in peace, and proves it base and abominable in war. We cannot tell what the fate of Finland may be, but no more mournful spectacle could be presented...than that this splendid northern race should be at last worn down and reduced to servitude worse than death by the dull brutish force of overwhelming numbers."

Temperatures in Finland dropped below minus 40 degrees Celsius during the war. The Red Army at the time had a policy of not training its troops in temperatures lower than minus 15 Celsius.

One group of surrounded Soviet soldiers sent a message to their superiors: "We are dying, please pay our March wages to our families. Tell everyone that we died as heroes…we did not surrender."

During interrogation, one prisoner recalled being told he was to "liberate our [Finnish] worker friends from capitalism." The soldier soon realized he had been misled: "I can feel in my own skin how we were welcomed by those we came to 'free.'"

After weeks of devastating losses up and down the eastern edge of Finland, the Soviet command finally changed tactics and focused on capturing Helsinki in the country's well-defended south.

Incendiary cluster bombs were used by the Soviets against Finnish settlements made of wood.

With overwhelming numbers, the Soviets began forcing back the exhausted Finns. In March 1940, as Soviet troops entered the suburbs of Vyborg, the Finns had little choice but to accept harsh Soviet terms for an armistice.