Soviet Invasion of Poland 17 IX 1939 - Symbolic Diorama On 17 IX 1939, by virtue of the Secret Additional Protocol to the Molotov - Ribbentrop Pact, Soviet forces entered Poland. By doing this they backstabbed the Polish army defending against Germans. The diorama is a symbolic representation of that event - Polish forces defends against incoming Germans, while the civilians are leaving the village. Meanwhile the Red Army enters from the East.