Treaty of Dubysa

The Treaty of Dubysa or Treaty of Dubissa (Lithuanian: Dubysos sutartys) consisted of three legal acts formulated on 31 October 1382 between Jogaila, Grand Duke of Lithuania, with his brother Skirgaila and Konrad von Wallenrode, Marshal of the Teutonic Order. During the Lithuanian Civil War (1381–84), Teutonic Order helped Jogaila and Skirgaila to defeat their uncle Kęstutis and his son Vytautas. Trying to realize promises given by Jogaila during the war, Teutonic Order organized the negotiations for the treaty. The acts were signed after six days of negotiations on an island in the mouth of the Dubysa River. The treaty was never ratified and never came into effect. The civil war resumed in summer 1383.

In the first act Jogaila promised to baptize himself and convert the Grand Duchy of Lithuania to Christianity within four years.Samogitia, land that physically separated the Teutonic Order in Prussia from uniting with its branch in Livonia, was ceded to the Order up to the Dubysa River by the second act. It was the first time that during the 100-year crusade Lithuania gave up Samogitia. The third act formed a four-year military alliance – both sides promised to help each other against their enemies. Jogaila also agreed not to start a war without the Order's approval. Such provisions were limiting Jogaila's sovereignty. Some historians even suggested that such agreement would establish a lord–vassal relationship.

All three acts (only two originals survive, the third is known from a transcript made in 1410) were signed by all sons of Algirdas and Uliana of Tver (Jogaila, Skirgaila, Kaributas, Lengvenis, Karigaila, Vygantas, and Švitrigaila) and by Hanul, a merchant from Vilnius who opened the city gates in June 1382, allowing Jogaila to depose Kęstutis. Uliana signed only the act granting Samogitia to the Order. Lithuanian historians Ignas Danilevičius and Ignas Jonynas raised doubts whether this act is authentic or a forgery from 1410s, but their thesis is not widely accepted.

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