In 1937, Stalin purged the majority of his top military officers, starting with [Marshal Tukhachevsky](https://military.wikia.org/wiki/Mikhail_Tukhachevsky)
This disorganized the Red Army, to say the least, and helped account for its later poor performance against Finland, in 1939-1940, and even later against the Nazis, immediately after the invasion in June, 1941.

How well did the Red Army perform during its (brief) 1939 invasion of Poland? (Apparently [they inflicted more Polish casualties than they lost of their own men.](https://en.wikipedia.org/wiki/Soviet_invasion_of_Poland#:%7E:text=On%2017%20September%201939%2C%20the,invaded%20Poland%20from%20the%20west.&text=The%20Red%20Army%2C%20which%20vastly,of%20war%20had%20been%20captured.)) Was the Red Army's performance "misleading" by being better than it was later? Did this episode expose weaknesses that foreshadowed the Red Army's later problems? Or was it a "trivial" passage that did not meaningfully test the Red Army?