Duchy of Lithuania Duchy of Lithuania Duchy of Lithuania (; ) was a state-territorial formation of ethnic Lithuanians, that existed from the 13th century until 1413. Most of the time it was a constituent part and a nucleus of the Grand Duchy of Lithuania. Other alternative names of the territorial formation, used in different periods, were Aukštaitija or Land of Lithuania (13th century), Duchy of Vilnius (14th – early 15th centuries), Lithuania Propria or simply Lithuania (in a narrow sense). The formation emerged in the central and eastern part of the present-day Lithuania, known as Aukštaitija, as the Lietuva Land (). It is
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