After signing the German–Soviet Frontier Treaty (28 September 1939), which established the mutual border along the Bug River, the Politburo of the Central Committee of the Communist Party of the Soviet Union decided on October 1, 1939, that People's Assemblies of Western Ukraine and Western Belorussia should be called in Lviv (for Western Ukraine), and Belastok (for Western Belorussia). The task of these bodies was to urge Moscow to incorporate the land into the Soviet Union. Furthermore, a People's Assembly of Poland had been planned, for the areas around Lublin, Siedlce, and Łomża, which were to have been annexed by the Soviets. However, after some changes in the Nazi–Soviet Pact (see German–Soviet Frontier Treaty), those areas were occupied by Nazi Germany.