The territorial expansion of the Soviet Union was the result of imperialism present in the Communist Doctrine, and an ideological attempt to expand the Bolshevik revolution. In 1920, the onset of the Red Army in the western part of Europe was stopped by the Polish army, which devoted himself to the protection of the Polish capital of Warsaw, and then crossed the counteroffensive, displacing the aggressor from Polish lands. The success of the Polish army stopped the Bolshevik expansion, but did not stop the construction process of the Soviet Empire. In the 1920s and 1930s, under the control of the Soviets, there were areas of today's Ukraine, Belarus, Kazakhstan, Georgia, Azerbaijan, Armenia, Tajikistan, Turkmenistan, Uzbekistan and Kyrgyzstan. In 1938-39, the Red Army also had conquered in Central and East Asia, fighting with Japanese troops.
On the eve of the beginning of World War II, the Soviet Union signed a political and military agreement with Nazi Germany. The Molotov Ribbentrop Pact became the beginning of the joint aggression of both totalitarian states aimed primarily against Poland. At the same time, both sides divided the spheres of influence. Ultimately, according to Soviet-German agreements, the tips should have taken control of the eastern part of Poland and the Baltic countries - Lithuania, Latvia and Estonia. The USSR was also allowed to act against Finland.
In September 1939, the German and Soviet troops committed joint aggression against Poland. In accordance with further agreements, Polish lands were divided by setting the border along the River San, Pisa and Narev rivers. This border remained before the German attack on the USSR in June 1941 from a formal point of view, the territory of Eastern Poland was included in the Soviet Union and functioned as elements of the Belarusian and Ukrainian SSR. The occupation authorities almost immediately established the Soviet administration and began to actively plunder Polish land. The struggle against the Polish language and the Catholic religion, the persecution of the Polish intelligentsia began. Soviet soldiers began mass arrests of Poles, which were considered a threat to the communist system.
Repressions were led by the NKVD staff, primarily against military, clergy, officials and representatives of professions considered "intellectual". In many cases, mass murders took place. Polyakov was put in prisons and sent the Gulag system to Soviet concentration camp. More than 0.5 million Poles were arrested. In addition, in 1939-1941, a number of operations were carried out to move to the eastern border of the Soviet Union, as a result of which up to 1 million people were sent to the camps. Pınup