By the treaty of April 16, 1922, the Soviet Union obtained de jure recognition from Germany, including mutual cancellation of financial claims and most-favored-nation treatment. It established diplomatic relations with the Weimar Republic on July 23, 1923.
From that time until the breaking of diplomatic relations on June 22, 1941, the Soviet Union not only maintained normal diplomatic and economic relations with Germany but also assisted in building up a new German war machine.
Official records of the Weimar Republic show that from 1922 to 1934 the Soviet Union enabled Germany to violate secretly the disarmament provisions of the Versailles Treaty by training German fliers and tankmen in special schools on Soviet soil and by furnishing Germany with ammunition, aircraft engines, and poison gases.
On April 24, 1926, the Soviet Union signed a neutrality pact with Germany. This pact provided one party was to remain neutral if the other were attacked. Each nation promised not to join any coalition against the other in case of attack or to join in economic sanctions against the other if imposed by the League of Nations. This neutrality pact was extended on June 24, 1931, and this extension was ratified on May 5, 1933, after Hitler's assumption of power.
Despite the change of attitude by the U.S.S.R. after Hitler's suppression of the German Communist Party, there was no lessening of the large-scale German-Soviet economic collaboration. This estrangement was accompanied by a temporary improvement of relations between the U.S.S.R. and the democratic countries. The U.S.S.R. was admitted to the League of Nations in 1934 and concluded a mutual assistance pact with France in 1935.
Following the disillusionment of the Munich conference of 1938, the French and British Governments sought to block German aggression toward the East. They guaranteed the integrity of Poland and Rumania early in 1939. In April 1939 the United Kingdom and France, on their own initiative, began military negotiations with the U.S.S.R. which continued into the summer.
These Western negotiations with the U.S.S.R. were undercut by the signature of the Molotov-Ribbentrop agreements of August 23, 1939, which replaced the Soviet-German neutrality pact of 1926 with a 10-year nonaggression pact. The new agreements provided the necessary guaranties for coordinated German and Soviet aggression in Eastern Europe. The immediate victims were Finland, Poland, Rumania, and the Baltic States.
The German attack on Poland came 8 days after the signature of the Nazi-Soviet pact. Great Britain and France, faithful to their obligations to Poland, declared war on Germany on September 3, 1939. The U.S.S.R. occupied major parts of Poland on September 17, 1939.
In a note to the Polish Government on September 16, 1939, the Soviet Union said:
The Polish-German war has revealed the internal insolvency of the Polish State. The Polish Government has fallen to pieces and shows no sign of life. This means that the Polish State and its Government have virtually ceased to operate.
Treaties concluded between the U.S.S.R. and Poland have thereby ceased to operate. Abandoned to her fate and left without leadership, Poland has become a fertile field for any accidental and unexpected contingency which may create a menace to the U.S.S.R.