The People's Seimas was a puppet legislature organized in order to give legal sanction the occupation and annexation of Lithuania by the Soviet Union. After the Soviet ultimatum in June 1940, a new pro-Soviet government was formed, known as the People's Government. The new government dismissed the Fourth Seimas and announced elections to the People's Seimas. The elections were heavily rigged, and resulted in a chamber composed entirely of Communists and Communist sympathizers. The new parliament unanimously adopted a resolution proclaiming the Lithuanian Soviet Socialist Republic and petitioned for admission to the Soviet Union as a constituent republic. The Supreme Soviet of the USSR accepted the Lithuanian petition on August 3, 1940. The People's Seimas adopted a new constitution, a close copy of the 1936 Soviet Constitution, on August 25 and renamed itself to the Supreme Soviet of the Lithuanian SSR.

Vincas Vitkauskas was a Lithuanian general. He became commander of the Lithuanian Army after the resignation of Stasys Raštikis in January 1940. In this capacity, Vitkauskas opposed armed resistance to the Soviet occupation in June 1940 and subsequently collaborated with the new Soviet regime.