Sigismund (1368-1437), Holy Roman emperor (1411-1437) and king of Hungary (1387-1437) and Bohemia (1419-1437), the son of Holy Roman Emperor Charles IV. In 1385 he married Queen Mary of Hungary, thus acceding to the throne of Hungary two years later. In 1396 he led a great army of Crusaders from many parts of Europe against the Turks; the latter, under the Ottoman sultan Bayazid I, inflicted a crushing defeat upon Sigismund’s forces at Nicopolis (now Nikopol), Bulgaria. Upon the death of Holy Roman Emperor Rupert, Sigismund was elected to succeed him, but he did not receive formal coronation at the hands of the pope until 1433. In 1414 Sigismund persuaded the antipope John XXIII to convoke the Council of Constance at which a long-standing dispute over the papal succession was settled and ecclesiastical reforms were instituted. The council also tried the Bohemian religious reformer Jan Hus (John Huss) and condemned and executed him as a heretic. Sigismund succeeded to the throne of Bohemia in 1419. His power in Bohemia was never more than nominal, however, as the Bohemians believed him guilty of complicity in the death of Hus and repeatedly rose in arms against him (see Hussite Wars).