German–Soviet Boundary and Friendship Treaty

The German–Soviet Boundary and Friendship Treaty was a second supplementary protocol of the Molotov–Ribbentrop Pact of 23 August 1939. It was a secret clause as amended on 28 September 1939 by Nazi Germany and the Soviet Union after their joint invasion and occupation of sovereign Poland.

Source: Wikipedia — German–Soviet Boundary and Friendship Treaty (CC BY-SA 4.0)