Russia's military struggles in Ukraine are starting to look like a bloody Soviet attack on a smaller neighbor during World War II

• The Russian military's performance in Ukraine has raised doubts about its capabilities.
• The war has also drawn comparisons to the Winter War, when the Soviets attacked Finland in 1939.

Russia's heavy losses and slow progress in Ukraine have raised doubts about the strength and competence of the Russian military.

US officials estimate that several thousand Russian troops have been killed during the invasion, now in its third week, and videos of Russian tanks and other vehicles being destroyed in Ukrainian attacks or being carted off by Ukrainians have made the losses hard to hide. Reports that several high-ranking Russian officers have been killed on the front lines adds to the sense of disarray.

Russia's poor performance, and Ukraine's surprisingly strong resistance, have drawn a number of comparisons to the Winter War between the Soviet Union and Finland between 1939 and 1940.

During that frigid 105-day war, the Finnish military inflicted severe casualties on the massive Red Army.

There's reason to be cautious about such comparisons, according to Michael Kofman, research program director in the Russia Studies Program at CNA, a think tank.

The Winter War, Kofman told War on the Rocks on March 6, "led to the belief that maybe the Soviet military in some ways is just terrible," with a lot of troops and material but "fairly low" combat efficacy.

Finland ultimately lost that war, and German perceptions of Soviet military weakness proved disastrously wrong.

The Winter War

Launched by the Soviets early on November 30, 1939, the Winter War was prompted by Moscow's failure to get the Finns to give up their border territory near Leningrad and allow Soviet troops to be stationed in Finland.

On paper, it should have been no contest. Before the war, Finland's entire military numbered around 280,000 men, with only 400 artillery pieces, 32 tanks, and 75 combat-capable aircraft.

By comparison, the Soviets' Leningrad Military District alone had 500,000 men, 5,700 field guns, 6,500 tanks, and 3,800 aircraft.

Soviet leader Josef Stalin was so confident that he rejected a cautious plan presented by then-Red Army Chief of Staff Boris Shaposhnikov that called for massive, concentrated thrust through Finland's main line of defense.

Stalin instead selected a plan that called for a blitz across almost all of the 800-mile Soviet-Finnish border — similar to Germany's blitzkrieg into Poland.

Soviet planners believed the entire operation would last about two weeks and equipped their soldiers accordingly. But the Finns more than held their own during the first six weeks of the war.

The Red Army consistently failed to breach Finland's Mannerheim Line in the Karelian Isthmus, a stretch of land west of Leningrad, while Soviet offensives in central Finland were chewed up by Finnish soldiers using guerrilla tactics.

Long Red Army columns confined to the few existing roads and its advances through dense forests exposed it in a way that negated its numerical advantage.

Constant snow and freezing weather favored the Finns, who employed ski troops and winter camouflage. Soviet commanders, confident in a quick victory, did not initially equip their troops with similar gear.

The Finns would cut off and surround Red Army columns, a tactic they called "motti," and then destroy the Soviets piecemeal with devastating efficiency.

At the Battle of Tolvajärvi, 5,000 Soviets were killed, compared to about 630 Finns. There were similar outcomes at the battles of Suomussalmi and Raate Road, with a Soviet division effectively destroyed at each.

By February, Stalin implemented changes. Shaposhnikov was given command of forces in Finland, the Red Army was reorganized, and the Soviet plan was restructured to focus on a concentrated drive through the Mannerheim Line.

A massive offensive finally broke through in February 1940. The Finns, with fewer troops and resources, faced complete defeat and had no option but to agree to negotiations.

'A paper tiger'

In the Moscow Peace Treaty signed on March 12, 1940, Finland ceded about 10% of its territory to the Soviets, including all of the Karelian Isthmus and the northern region of Petsamo, cutting Finland off from the Barents Sea.

It came at a dreadful cost for the Soviets. In 105 days, as many as 140,000 Red Army soldiers were killed and more than 3,500 tanks and 1,000 aircraft were destroyed. About 26,000 Finns were killed, while Finland lost 30 tanks and 62 aircraft.

The Winter War had ramifications outside of Finland.

The Red Army's poor performance, coupled with the disastrous effects of Stalin's military purges and a similarly poor performance in the Polish-Soviet War years earlier, solidified Hitler's belief that the Red Army was incapable of fighting the might of the Wehrmacht.

Before launching his attack on the Soviets in June 1941, Hitler reportedly told his generals that "we have only to kick in the door and the whole rotten structure will come crashing down."

Hitler's confidence was misplaced. The Nazis inflicted over a million casualties on the Soviets in the first stages of their invasion of the USSR, but the Red Army — with massive help from its allies — rallied, reorganized, and fought all the way into Berlin.

Western aid and the lessons of the Winter War turned the Red Army into a more powerful and more capable force than it was in 1939, as both the Germans and the Finns saw first-hand.

Judging the Russian military's capabilities based on its performance in Ukraine may also be misguided, Kofman said this month, warning that "you definitely don't want to end up where Germany ended up."

"I'm worried we're going to walk away with a decent assessment of all the problems in the Russian military but also with a wrongheaded notion that it's a paper tiger or the Russian military would fight in a regional context in a high-end contingency against NATO in exactly the same way they tried to perform this botched sort of regime-change operation," Kofman said.