From September 17, 1939 Poland had a second enemy, the USSR. Pursuant to the Molotov-Ribbentrop Pact, the Soviet Union occupied the territory of Eastern Poland. This explains why the Polish Government in Exile under General Wladylsaw Sikorski trumpeted the theory of “two enemies” striving to push, albeit ultimately unsuccessfully, international public opinion to condemn the USSR. Germany’s June 22, 1941 attack on the Soviet Union radically altered the situation. Of the original two enemies only one remained: Nazi Germany, and the Soviet Union became an ally. Sikorski was also practically forced by Prime Minister Winston Churchill to sign a pact with Moscow (The Sikorski-Maisky Pact of July 30, 1941) on very unfavorable terms. This document enabled the reestablishment of diplomatic relations and the establishment of a Polish Army in the USSR, but it did not deal with the matter of Poland’s eastern border. There was also no explanation as to the whereabouts of several thousand Polish officers, who were interned by the Soviet Union in September 1939. This was not surprising, given the fact that in the Spring of 1940 the NKVD, on the authorities of the Soviet party and government, murdered these Polish officers in Katyn, Miednoj and Charkov.
While officially maintaining diplomatic relations with the Polish government in exile in London, Stalin kept Polish Communists in reserve, planning to deploy them in the right moment to establish authority over Poland. The time came when the USSR’s military situation improved, and Stalin’s position with respect to the Big Three strengthened to such a degree that he could begin to demand concessions from the Western Allies. (See Allies and the Polish Question). The first step was to allow the Polish Army in the USSR (Anders’ Army) to evacuate from the Soviet Union in 1942. Next, using the government in exile’s request to the International Committee of the Red Cross to investigate the graves discovered in the Katyn Forest as pretext, Stalin broke off relations with Poland’s London government on April 25, 1943. Katyn (the other places of mass executions were not discovered until half a century later) also influenced how the USSR was perceived in occupied Poland, greatly increasing anti-Soviet sentiment. Underground leadership began to consider the possibility of a Soviet occupation as ever more likely. Although the official orders for Operation Tempest (See )required that Red Army forces be met as allies, a secret underground structure was being built (Organization “NIE”). This concern was justified: Home Army units, which considerably aided in the liberation of Lviv and Vilnius in July 1944, were disarmed, and their commanders and soldiers arrested.
The time for Poland’s communists had dawned. Stalin had first allowed them to form an Army (See From Lenino…) Next – after the army crossed the Bug River in July 1944, which was meant to serve as Poland’s new, modified eastern boundary – they established a faux government. Meanwhile the NKVD efficiently assisted in liquidating any opposition. But there was a second side to the coin: Polish society, even with justified concerns regarding the Red Army’s actions, saw the entry of Soviet forces into Poland as a liberation from the five long years of German occupation. Some 600,000 Soviet Soldiers perished on the current territory of Poland.