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
History of Lithuania 1410, but the allied armies failed to take Marienburg, the Knights' fortress-capital. Nevertheless, the unprecedented total battlefield victory against the Knights permanently removed the threat that they had posed to Lithuania's existence for centuries. The Peace of Thorn (1411) allowed Lithuania to recover Samogotia, but only until the deaths of Jogaila and Vytautas, and the Knights had to pay a large monetary reparation. The Union of Horodło (1413) incorporated Lithuania into Poland again, but only as a formality. In practical terms, Lithuania became an equal partner with Poland, because each country was obliged to choose its future ruler only with