Tratado de Paz de Moscú
The Karelo-Finnish Soviet Socialist Republic was established by the Soviet government on 31 March 1940 by merging the KASSR with the Finnish Democratic Republic. The latter was created in territory ceded by Finland in the Winter War by the Moscow Peace Treaty, namely the Karelian Isthmus and Ladoga Karelia, including the cities of Viipuri and Sortavala.