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 Minor was found which indicated that in 1990, the Soviet leadership was prepared to negotiate the return of Kaliningrad to Germany against payment. The proposal was declined by German diplomats. After the dissolution of the Soviet Union, the Kaliningrad Oblast has become an exclave of Russia. Lithuania, Germany, and Poland lay no official claims to the region at this time. Of the portion of Lithuania Minor that is currently in Poland, Gołdap, (), the seat of Gołdap County, is the largest municipality of the region within the Polish state, making it the de-facto capital of Polish Lithuania Minor. Unlike the area