1940 Soviet ultimatum to Lithuania

The Soviet Union issued an ultimatum to Lithuania before midnight of June 14, 1940. The Soviets, using a formal pretext, demanded to allow an unspecified number of Soviet soldiers to enter the Lithuanian territory and to form a new pro-Soviet government (later known as the "People's Government"). The ultimatum and subsequent incorporation of Lithuania into the Soviet Union stemmed from the division of Eastern Europe into the German and Russian spheres of influence in the Molotov–Ribbentrop Pact of August 1939. Lithuania, along with Latvia and Estonia, fell into the Russian sphere. According to the Soviet–Lithuanian Mutual Assistance Treaty of October 1939, Lithuania agreed to allow some 20,000 of Soviets troops to be stationed at several bases within Lithuania in exchange for a portion of the Vilnius Region. Further Soviet actions to establish its dominance in its sphere of influence were delayed by the Winter War with Finland and resumed in spring 1940 when Germany was making rapid advances in western Europe. Despite the threat to the independence, Lithuanian authorities did little to plan for contingencies and were unprepared for the ultimatum.

With Soviet troops already stationed in the country according to the Mutual Assistance Treaty, it was impossible to mount effective military resistance. On June 15, Lithuania unconditionally accepted the ultimatum and lost its independence. The Soviets sought to show the world that this was not a military occupation and annexation, but a legitimate socialist revolution, initiated by the local population demanding to join the Soviet Union. Therefore, the Soviets followed semi-legal procedures: they took control of the government institutions, installed a new puppet government, and carried out show elections to the People's Seimas. During its first session, the Seimas proclaimed creation of the Lithuanian Soviet Socialist Republic and petitioned to be admitted into the Soviet Union. The petition was officially accepted by the Supreme Soviet of the Soviet Union on August 3, 1940. At the same time almost identical processes took place in Latvia and Estonia. Lithuania would not regain its independence until the proclamation of the Act of the Re-Establishment of the State of Lithuania on March 11, 1990.

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