Summary

Sigismund (Sigismont) Keistutovich (Lithuanian: Žygimantas Kęstutaitis, c. 1365-20 March 1440, Troki) was Prince of Mozyr (1385-1401), Novogrudok (1401-1406) and Starodub (1406-1432), Grand Duke of Lithuania from 1432 to 1440. Son of Prince Keistut of Troc and Samogitia from his marriage with Biruta, younger brother of Grand Duke Vitovt of Lithuania.

During the power struggle between Vitovt and Jagailo he was captured by the latter (1382-1384). In 1384 in Königsberg, together with Vitovt, he made a treaty with the Teutonic Order against Jagiello, but in 1386 he swore allegiance to him. In 1386 he and the other Gediminovichs were baptized according to the Catholic rite in Krakow. In 1389 he was sent by Vitovt to Prussia to negotiate with the Order against Yagaylo. By 1398 he was a hostage of the Grand Master in Marienburg. After his return he received the Starodubskoe principality (Severskoye) from Vitovt.

Took part in negotiations and the conclusion of agreements with the Teutonic Order in 1398, 1411, 1422, 1431, a union with Poland. He took part in the battle of Vorskla (1399) and the battle of Grunwald (1410). Under Vitovt's rule had no political influence, he supported his brother.

The internecine war

After Vitovt died and Svidrigailo was elected grand duke in 1432, Sigismund participated in a conspiracy against him, but Svidrigailo managed to flee to Polotsk. With the support of the Poles, Sigismund was elected grand duke, and his power was recognized by Vilna, Troki, Kovno, Zhemaitija, Grodno, Minsk, Novogrudok, and Brest was subjugated by force. The remaining lands remained loyal to Svidrigailo, who entrenched himself in Vitebsk.

An internecine struggle began between Svidrigailo and Sigismund. In order to attract the feudal lords of the anti-Polish party to his side, Sigismund extended all the rights given to the feudal lords who had converted to Catholicism to all the feudal lords of the GDL regardless of their creed. But a significant part of the nobles still did not support Sigismund, because he was pursuing a policy of subjecting the GDL to Poland. Svidrigajlo suffered a heavy defeat at the battle of Vilkomir (1435), and soon (1437) Sigismund became the sovereign Grand Duke.

Murder

Sigismund was too suspicious, probably knowing that the anti-Polish party still abounds in supporters, so all the time looking for conspirators, even imaginary, severely punished them, confiscated estates, sentenced to death. This even led to rumors that he wanted to exterminate all the princes and boyars. A conspiracy of princes Ivan and Alexander Chartoryisky, Jan Dovgerd (governor of Vilnius) and Peter Lyalush (governor of Troitsk) was organized against him - all four were Catholics, who belonged to the anti-Polish party and were associated with Svidrigailo. As a result of the conspiracy, Sigismund was murdered in the Troki Peninsula Castle.

Sources

1. Sigismund Kęstutaitis
2. Сигизмунд Кейстутович
3. 1,0 1,1 Darryl Roger Lundy: (Αγγλικά) The Peerage.
4. Kallio 2009, s. 69
5. Kallio 2009, s. 70
6. Grzegorz Błaszczyk, Dzieje stosunków polsko-litewskich tom II: Od Krewa do Lublina, część 1, Poznań 2007, s. 27.