Władysław II Jagiełło

Born Jogaila around 1352 or 1362, he became Grand Duke of Lithuania in 1377, ruling a polytheist realm on Catholicism's frontier. In 1386 he converted, took the name Władysław, married the young Queen Jadwiga in Kraków, and became King of Poland - a political baptism that brought Lithuania into the Catholic fold the following year. He ruled jointly with Jadwiga until her death in 1399, then alone for thirty-five more years, ceding the Grand Duchy to his cousin Vytautas in 1401 while retaining supreme authority. The Polish-Lithuanian alliance he forged met the Teutonic Order at Grunwald in 1410 and won decisively, a victory that secured the borders and announced the union as a European power. He died in 1434, leaving a dynasty - the Jagiellonians - that would rule both states until 1572 and shape the continent's late medieval order.