We were completely disoriented, we had no idea about the Ribbentrop-Molotw pact. We did not know id they [The Soviet army]were coming to join us in our fight against the Germans or if this was a new attack. When we started to fight and the Soviet planes started to drop bombs on us, it became clear what was going on […..]
-Stanislaw Matkowski, Polish Army Officer whose unit was stationed on the Polish-Soviet border in September, 1939
It became apparent that all that was needed was an initial attack of the German Army and, after that, the attacke of the Soviet [Army]; in order to leave nothing of [Poland] this monstrous bastard of the Treaty of Versailles…
-Wyacheslav Molotov, Soviet Prime Minister in his speech to the Supreme Soviet On September 31,1939 about the German-Soviet invasion of Poland
See video below (an excerpt of a much longer film):