High Quality Content by WIKIPEDIA articles! After signing the German-Soviet Nonaggression Treaty in 1939, the Soviet Union took part in the invasion of Poland and its subsequent dismemberment. The Soviet authorities declared Poland non-existent and all former Polish citizens from the areas annexed by USSR were treated as if they were Soviet citizens. This resulted in approximately 2 million Polish citizens (including a quarter of a Millions POWs and 1.5 million deportees) being arrested and imprisoned by the NKVD and other Soviet authorities. However, with the outbreak of the Soviet-German War in 1941 the international situation of Soviet Union changed and Joseph Stalin started to seek help from other countries opposing Germany. Strongly encouraged by British Foreign Office diplomat Anthony Eden, Sikorski on 5th July, 1941, opened negotiations with the Soviet ambassador to London, Ivan Mayski, to re-establish diplomatic relations between Poland and the Soviet Union. Sikorski was the architect of the agreement reached by both governments, that was finally signed on 30th July, 1941. A further military alliance was signed in Moscow on 14th August 1941.