The first major change in the international relations of Russia was the signing of the Treaty of Brest-Litovsk in 1918. This brought Russia out of World War I, however in the aftermath of the Russian Revolutions, especially the October Revolution, the Russian Civil War began and its former allies, dreading Bolshevism and having felt betrayed by the Russian retreat from WWI and subsequent dishonouring of tsarist debts, sided with the White Russians in the new war. Despite the Red Russians gaining victory in the end, thereby preserving the revolutionary government but also leaving the new Soviet Union without international partners or official recognition.
The first major breakthrough for the Soviet Union came in the form of new relations with the postwar Germany with the Treaty of Rapallo, signed on 29 July 1922. Its goals, which were reconfirmed with the Treaty of Berlin in April 1926, stipulated the revocation of diplomatic animosity and financial obligations, but in reality signalled the beginning of a much more productive relationship. It led to the establishment of powerful military and economic partnerships, as well as the Soviet Union and Germany becoming more acknowledged on the international level. It also resulted in the countries gaining military hardware and experience, in violation of the Treaty of Versailles in the case of Germany.
With a new government in the Nazi Party, led by Adolf Hitler, Russo-German relations were officially brought to an end in May 1933. With its foreign policy, and that of its neighbours, in disarray, the Soviet Union initiated relations with the United States in November of that year. While small-scale commerce had been occurring even when their relations were not as amicable, the recognition by the United States of the Soviet Union also brought an end to the ideological battle between the two, the US having been a long-standing stronghold against communism. This contributed strongly to the Soviet Union’s admission into the League of Nations in 1934.
However, only six later the Soviet Union astonished the world community with the Nazi-Soviet Non-Aggression Pact, authorised on 19 August 1939 as a result of the threat of fascism, especially from Germany, the volatility of the European continent and Joseph Stalin’s distrust of Britain and France, especially after their leaders appeased Hitler and ceded Czechoslovakia’s Sudetenland in 1938, The agreement, which not only specified mutual neutrality but also defined their spheres of influence, gave the Soviet Union both enough time for its armed forces to prepare for inevitable war with Germany but also allowed the invasion of its neighbours, including Finland. However, in what would become the Winter War, Soviet forces, superior in both numbers and technology, gained only a pyrrhic victory, influencing Hitler to arrange and commence Operation Barbarossa, the invasion of Russia, in June 1941.
Operation Barbarossa had several drastic effects for the Soviet Union. It not only marked its official entry into World War II, but also prompted offers of aid from the United States and Britain, who extended diplomacy and the Lend-Lease programme to the Soviet Union. With its acceptance of assistance, the Soviet Union was formally an Allied Power, a position maintained until the end of WWII and the beginning of the Cold War.