The Soviet Union in World War II

Engaged in a border war with Japan in the Far East and fearing the German advance in the west, the Soviet government in 1939 began secret negotiations for a non-aggression pact with Germany, meanwhile continuing negotiations, begun earlier, with France and Britain for an alliance against Germany. In August 1939 it suddenly announced the conclusion of a Soviet-German pact of friendship and non-aggression. This pact contained a secret clause providing for the partition of Poland and for Soviet and German spheres of influence in Eastern Europe. On September 1 Germany invaded Poland, thereby provoking declarations of war by Great Britain and France and launching World War II. Sixteen days later, the Red Army crossed the Polish frontier, took possession of eastern Poland, and began the Sovietization of the occupied areas. Hundreds of thousands of Poles were deported to Siberia. On September 29, the German and Soviet governments signed a treaty demarcating their so-called spheres of interest in Poland. The treaty acknowledged the supremacy of each power in its respective sphere and provided for joint resistance to interference from third parties.

The pact with Hitler signalled the opening of a new phase in the development of the USSR. In the immediately preceding years the central emphasis of Soviet policy had been on "building socialism", that is, on the industrialization of the country. The seizure of eastern Poland was the first of a series of territorial annexations that launched a new expansionist phase of Soviet policy. The Polish annexation was soon followed by domination of Estonia, Latvia, and Lithuania. Non-aggression pacts, imposed on the Baltic states, gave the Soviet Union the right to station troops on their soil.

The Winter War with Finland

Also during the fall of 1939, the Soviet government demanded of Finland that it cede territory on the Karelian Isthmus north-east of Leningrad and permit the USSR to establish a naval base on the Finnish coast of the Gulf of Finland. Rejection by the Finnish government of the Soviet demands led to the undeclared Russo-Finnish War, which began with the Soviet invasion of Finland on November 30, 1939. After a valiant but futile resistance, the Finns were overcome by the immensely superior forces of the Soviet Union. The war ended on March 12, 1940.