The Treaty of Rapallo, pursuant to which Germany and the Soviet Union re-establish diplomatic relations, is signed.

The Treaty of Rapallo was an agreement signed on 16 April 1922 between the German Reich and Soviet Russia under which both renounced all territorial and financial claims against each other and opened friendly diplomatic relations. The treaty was negotiated by Russian Foreign Minister Georgi Chicherin and German Foreign Minister Walther Rathenau. It was a major victory for Russia especially and also Germany, and a major disappointment to France and the United Kingdom. The term "spirit of Rapallo" was used for an improvement in friendly relations between Germany and Russia.

The Weimar Republic, officially known as the German Reich, was the German state from 1919 to 1933, during which it was a constitutional republic for the first time in history; hence it is also referred to, and unofficially proclaimed itself, as the German Republic. The period's informal name is derived from the city of Weimar, which hosted the constituent assembly that established its government. In English, the republic was usually simply called "Germany", with "Weimar Republic" not commonly used until the 1930s. The Weimar Republic had a semi-presidential system.

The Union of Soviet Socialist Republics (USSR), commonly known as the Soviet Union, was a transcontinental country that spanned much of Eurasia from 1922 until it dissolved in 1991. During its existence, it was the largest country by area, extending across eleven time zones and sharing borders with twelve countries, and the third-most populous country. An overall successor to the Russian Empire, it was nominally organized as a federal union of national republics, the largest and most populous of which was the Russian SFSR. In practice, its government and economy were highly centralized. As a one-party state governed by the Communist Party of the Soviet Union (CPSU), it was the flagship communist state. Its capital and largest city was Moscow.