Temporary capital of Lithuania during the invasion of Poland, to Lithuania according to the Soviet–Lithuanian Mutual Assistance Treaty. Since then Vilnius has been the capital of the Lithuanian SSR and then independent Lithuania. Lithuania refused to have diplomatic relations between Poland and Lithuania until the ultimatum of 1938. Railroad traffic, telegraph lines or even mail could not cross the Polish–Lithuanian border. Lithuania continued to declare Vilnius as its capital in all official documents, including the constitution. Since the city was controlled by Poland, all Lithuanian authorities were transferred to the city of Kaunas, which became the seat of the government. To reconcile reality with
Lithuania July 1991, Soviet paramilitaries killed seven Lithuanian border guards on the Belarusian border in what became known as the Medininkai Massacre. On 17 September 1991, Lithuania was admitted to the United Nations. On 25 October 1992, the citizens of Lithuania voted in the referendum to adopt the current constitution. On 14 February 1993, during the direct general elections, Algirdas Brazauskas became the first president after the restoration of independence of Lithuania. On 31 August 1993, the last units of the Soviet Army left the territory of Lithuania. Since 29 March 2004, Lithuania has been part of the NATO. On 1