Сигизмунд Кейстутович
In the 1430s he supported Grand Duke Švitrigaila and the Teutonic Order in the civil war against Sigismund Kęstutaitis and war against Poland. On 30 November 1432 he was defeated at Kopestrzyn (or "kopersztyn") by Ruthenian voivode Wincenty z Szamotuł, Feodor escaped.