World War II: During the Continuation War, the Soviet Union demands unconditional surrender from Finland during the beginning of partially successful Vyborg–Petrozavodsk Offensive. The Finnish government refuses.

The Continuation War, also known as the Second Soviet–Finnish War, was a conflict fought by Finland and Nazi Germany against the Soviet Union during World War II. It began with a Finnish declaration of war on 25 June 1941 and ended on 19 September 1944 with the Moscow Armistice. The Soviet Union and Finland had previously fought the Winter War from 1939 to 1940, which ended with the Soviet failure to conquer Finland and the Moscow Peace Treaty. Numerous reasons have been proposed for the Finnish decision to invade, with regaining territory lost during the Winter War regarded as the most common. Other justifications for the conflict include Finnish President Risto Ryti's vision of a Greater Finland and Commander-in-Chief Carl Gustaf Emil Mannerheim's desire to annex East Karelia.

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.

The Vyborg–Petrozavodsk offensive or Karelian offensive was a strategic operation by the Soviet Leningrad and Karelian Fronts against Finland on the Karelian Isthmus and East Karelia fronts of the Continuation War, on the Eastern Front of World War II. The Soviet forces captured East Karelia and Vyborg/Viipuri. After that, however, the fighting reached a stalemate.