After the demise of
Gediminas in December 1337, the
Duchy of Lithuania was divided into two parts: Grand Duke
Algirdas ruled
Vilnius and the Eastern
Aukštaitija while his brother
Kęstutis received the Duchy of Trakai. The ruler of the
Duchy of Vilnius also was the
Grand Duke of Lithuania.
Lithuanian Civil Wars 1381–1384 In 1382, during the
Lithuanian Civil War, Kęstutis was imprisoned at the
Kreva Castle and died. His nephew
Skirgaila was named the new Duke of Trakai by his brother Grand Duke
Jogaila.
1389–1392 Vytautas, son of Kęstutis, then waged
a new Lithuanian Civil War to regain his patrimony in Trakai and seize power in Lithuania. The war was ended by the
Ostrów Agreement on August 4, 1392. The agreement transferred the Duchy from Skirgaila to Vytautas.
Union of Horodło in 1413 On October 2, 1413,
Vilnius and
Trakai Voivodeships were created by the
Union of Horodło from the Duchy of Trakai. The voivodeships were ruled by an appointed official and not by the dukes. ==Geography==