Kęstutis (, ; – 3 or 15 August 1382) was the Grand Duke of Lithuania. He was the Duke of Trakai and governed the Grand Duchy of Lithuania, 1342–1382, together with his brother Algirdas (until 1377), and with his nephew Jogaila (until 1381). The name "Kęstutis" is a derivative from the old form of the name Kęstas, which is a shortened version of such Lithuanian names as Kęstaras, Kęstautas (there kęs-ti means to cope). Historic writing sources reflect different Lithuanian pronunciation. Early life and division of power Kęstutis was the son of the Grand Duke Gediminas. His younger brother, Jaunutis, succeeded his father as Grand Duke of Lithuania. Together with his brother Algirdas, Kestutis conspired to remove Jaunutis from power. They were successful in their efforts. They divided their holdings into an eastern and western sphere of influence. The Duchy of Trakai was established in 1337 as a result. Kęstutis's efforts were concentrated in the west, while Algirdas' were concentrated in the eastern part of these territories. Kęstutis organized the defence of western Lithuania and Samogitia against the Teutonic Knights, and organized raids against the German Order. During Kęstutis's rule Teutonic raids into Lithuania reached the peak. Co-ruler of Lithuania Kęstutis employed different military as well as diplomatic means in his struggle on the western borders of the Grand Duchy of Lithuania. In 1349, to avoid further clashes with the Teutonic Order, he started negotiations with Pope Clement VI for the Christianization of Lithuania, receiving promises for royal crowns for him and his sons. Algirdas willingly remained aside of the business and was concerned with the order in the Ruthenian part of the state. The intermediary in the negotiations, Polish King Casimir III, made an unexpected assault on Volhynia and Brest in October 1349 that ruined the Kęstutis's plan. During the Polish-Lithuanian war for Volhynia, King Louis I of Hungary made a peace agreement with Kęstutis on 15 August 1351, according to which Kęstutis obliged himself to accept Christianity and provide the Kingdom of Hungary with military aid, in exchange for the royal crown. The agreement was approved with a pagan ritual by Kęstutis to convince the other side. In fact, Kęstutis had no intentions to comply with the agreement and ran away on their road to Buda. In crusaders' captivity In March 1361, Kęstutis along with his son Patrikas and brother - Grand Duke of Lithuania Algirdas destroyed and