Yes and that was a brilliant move on the part of Stalin. The Germans were thus tasked with all of the heavy lifting of destroying the Polish armed forces. By the time Stalin moved his divisions into eastern Poland, the country was already in shambles.
Yes, the exact same pattern that Stalin elected in seizing Manchuria from Japan a few days before the Japanese surrender, to later turn over to the Chinese Communists, after first looting heavy industry.
“The Germans were thus tasked with all of the heavy lifting of destroying the Polish armed forces. By the time Stalin moved his divisions into eastern Poland, the country was already in shambles.”
The Finnish War, though a victory in the end for the Soviets, exposed severe flaws in a Soviet Army run by Political Komissars, instead of military officers, many of which Stalin had already had murdered in the Purges.
Russia was in the middle of returning to a military ranks system when Poland happened, and would still be mired in it when Barbarossa came.
The very poor performance of the Soviet Army in Finland, in Poland, and again during the Romanian Crisis, encouraged Hitler to think that an attack on the Soviet Union would be successful.
The Red Army had 100,000 troops in Manchuria fighting the Japanese. They couldn’t have gone against Poland on September 1 if they had wanted to.