The Soviet Union invaded Finland on the 30th of November 1939 until the 13th of March 1940. The Soviets attacked with a total 998,100 men and the Finns attacked with 337,000 to 346,500 men. After Joseph Stalin's Great Purge, there was a lack of experienced officers in the Red Army, limiting his ability to capture the country. As proven time again, the Finns defending their homeland against a foreign invader by putting up a significant resistance. The Finns also had sufficient knowledge of their terrain and used tactics such as ski's to outmaneuver and flank their enemies. Despite these obstacles, the Soviets succeeded in capturing much of the country. However, it was only after they took massive casualties.