As a consequence of the Molotov–Ribbentrop Pact, on September 17, 1939, the Kresy territories were annexed by the Soviet Union (see Soviet invasion of Poland), and a significant part of the ethnic Polish population of "Kresy" was deported to other areas of the Soviet Union including Siberia and Kazakhstan. The new border between Nazi Germany and the Soviet Union was re-designated by the German–Soviet Frontier Treaty, signed on September 29, 1939. After the elections to the People's Assemblies of Western Ukraine and Western Belarus, communist governments for Western Ukraine and Western Belarus were formed and immediately announced their intention of joining their respective republics to the Soviet Union (see also Territories of Poland annexed by the Soviet Union). After the German invasion of the USSR, the southeastern part of "Kresy" was absorbed into Greater Germany's General Government, whereas the rest was integrated with the Reichskommissariats Ostland and Ukraine. In 1943–1944, units of the Ukrainian Insurgent Army, with the help of Ukrainian peasants, carried out mass exterminations of Poles living in southeastern "Kresy" (see Massacres of Poles in Wołyń).