In 1939, the Soviet Union made territorial claims to Finland, but Finland refused, so the Soviet Union sent an army of 260,000 people to attack Finland. Finland, however, was able to hold back the Soviet offensive with only 90,000 men, and caused the Soviet army to lose many soldiers. This was the best and only battle that Finland fought in World War II - the Winter War.

Later, the Soviet army continued to increase its troops. Although Finland’s troops had good mobility and strong combat effectiveness, they could not stop the Soviet army from pressing on the border. Finally, the Soviet Union paid a heavy price in exchange for the cession of Finland. part of the territory.