Question

what was signed in 1939 by hitler and stalin

Answer 1

The Molotov–Ribbentrop Pact, (also known as the Nazi–Soviet Pact), was a non-aggression pact signed between Nazi Germany and the Soviet Union in Moscow on 23 August 1939.

Answer 2

On August 23, 1939, Hitler and Stalin signed the German-Soviet Nonaggression Pact.

The name of the pact is quite obvious for what it's for. The Soviet Union (Stalin) and Germany (Hitler) signed a nonaggression pact. Hitler only wanted to sign the pact with the Soviet Union to invade Poland (which triggered the beginning of WWII). The pact stated most of the simple things: no attacking each other, no joining groups of powers that threaten either one of the two parties, etc.