Lithuanian Soviet Socialist Republic

The Lithuanian Soviet Socialist Republic (Lithuanian SSR; Lithuanian: Lietuvos Tarybų Socialistinė Respublika; Russian: Литовская Советская Социалистическая Республика, romanized: Litovskaya Sovetskaya Sotsialisticheskaya Respublika), also known as Soviet Lithuania or simply Lithuania, was de facto one of the constituent republics of the Soviet Union between 1940–1941 and 1944–1990. After 1946, its territory and borders mirrored those of today's Republic of Lithuania, with the exception of minor adjustments to its border with Belarus.

During World War II, the previously independent Republic of Lithuania was occupied by the Red Army on 16 June 1940, in conformity with the terms of the 23 August 1939 Molotov–Ribbentrop Pact, and established as a puppet state on 21 July. Between 1941 and 1944, the German invasion of the Soviet Union caused its de facto dissolution. However, with the retreat of the Germans in 1944–1945, Soviet hegemony was re-established and continued for forty-five years. As a result, many Western countries continued to recognize Lithuania as an independent, sovereign de jure state subject to international law, represented by the legations appointed by the pre-1940 Baltic states, which functioned in various places through the Lithuanian Diplomatic Service.

On 18 May 1989, the Lithuanian SSR declared itself to be a sovereign state, though still part of the USSR. On 11 March 1990, the Republic of Lithuania was re-established as an independent state, the first Soviet Republic to leave Moscow and leading other states to do so. Lithuania considered the Soviet occupation and annexation illegal and, like the other two Baltic States, claimed state continuity. This legal continuity has been recognised by most Western powers. The Soviet authorities considered the independence declaration illegal, but after the January Events in Lithuania and failed 1991 Soviet coup attempt in Moscow, the Soviet Union itself recognized Lithuanian independence on 6 September 1991.

On 23 August 1939, Nazi Germany and the Soviet Union signed the Molotov–Ribbentrop Pact, which contained agreements to divide Europe into spheres of influence, with Lithuania falling into Germany's sphere of influence. On 28 September 1939, the USSR and Germany signed the Frontier Treaty and its secret protocol, by which Lithuania was placed in the USSR's sphere of influence in exchange for Germany gaining an increased share of Polish territory, which had already been occupied. The next day, the USSR offered Lithuania an agreement on the establishment of Soviet military bases in its territory. During the negotiations, the Lithuanian delegation was told of the division of the spheres of influence. The Soviets threatened that if Lithuania refused to host the bases, Vilnius could be annexed to Belarus (at that time the majority of population in Vilnius and Vilnius region were Polish people). In these circumstances a Lithuania–USSR agreement on mutual assistance was signed in Moscow on 10 October 1939, allowing a Soviet military presence in Lithuania. A total of 18,786 Red Army troops were deployed at strategically important locations within the country: Alytus, Prienai, Gaižiūnai, and Naujoji Vilnia. This move effectively ended Lithuanian neutrality and brought it directly under Soviet influence.

While Germany was conducting its military campaign in Western Europe in May and June 1940, the USSR invaded the Baltic states. On 14 June 1940, an ultimatum was served to Lithuania on the alleged grounds of abduction of Red Army troops. The ultimatum said Lithuania should remove officials that the USSR found unsuitable (the Minister of the Interior and the Head of the Security Department in particular), replace the government, and allow an unlimited number of Red Army troops to enter the country. The acceptance of the ultimatum would have meant the loss of sovereignty, but Soviet foreign minister Vyacheslav Molotov declared to diplomat Juozas Urbšys that, whatever the reply may be, "troops will enter Lithuania tomorrow nonetheless". The ultimatum was a violation of every prior agreement between Lithuania and the USSR and of international law governing the relations of sovereign states.

The last session of the government of the Republic of Lithuania was called to discuss the ultimatum, with most members in favour of accepting it. On 15 June, President Antanas Smetona left for the West, expecting to return when the geopolitical situation changed, leaving Prime Minister Antanas Merkys in Lithuania. Before his departure, Smetona transferred most presidential duties to Merkys. Under the constitution, the prime minister became acting president whenever the president was unable to carry out his duties.

Meanwhile, the 8th and 11th armies of the USSR, comprising a total of 15 divisions, crossed the border. Flying squads took over the airports of Kaunas, Radviliškis, and Šiauliai. Regiments of the Red Army disarmed the Lithuanian military, took over its assets, and supported local communists. On 16 June, Merkys announced in a national radio broadcast that he had deposed Smetona, and was now president in his own right. On 17 June, the cabinet resolved that Smetona had effectively abandoned his post by leaving the country and confirmed Merkys as president without any qualifiers.

Later that day, under pressure from Moscow, on 17 June 1940, Merkys appointed Justas Paleckis prime minister and resigned soon after. Paleckis then assumed presidential duties, and Vincas Krėvė was appointed prime minister. The Communist Party was legalized again and began publication of its papers and staging meetings to support the new government. Opposition organizations and newspapers were outlawed, and ties abroad cut. On 14–15 July, elections took place for a "People's Seimas." The only contender was the Union of the Working People of Lithuania, a front for the Communists. Citizens were mandated to vote, and the results of the elections were likely falsified. At its first meeting on 21 July, the new People's Seimas declared that the Lithuanian people desired to join the Soviet Union. Accordingly, it unanimously changed Lithuania's official name to the Lithuanian Soviet Socialist Republic (LSSR) and formally petitioned to join the Soviet Union as a constituent republic. Resolutions to start the country's Sovietisation were passed the same day. On 3 August, a Lithuanian delegation of prominent public figures was dispatched to Moscow to sign the document by which Lithuania acceded to the USSR. After the signing, Lithuania was annexed to the USSR. On 25 August 1940, an extraordinary session of the People's Seimas reorganized itself as the provisional Supreme Soviet of the LSSR, ratified the Constitution of the LSSR, which in form and substance was similar to the 1936 Constitution of the Soviet Union.