World War II: The Battle of Romania begins with a major Soviet Union offensive.

The Battle of Romania in World War II comprised several operations in or around Romania in 1944, as part of the Eastern Front, in which the Soviet Army defeated Axis forces in the area, Romania changed sides, and Soviet and Romanian forces drove the Germans back into Hungary.

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.