John III Sobieski , Polish Jan Sobieski, (born Aug. 17, 1629, Olesko, Pol.—died June 17, 1696, Wilanów), Elective king of Poland (1674–96). Named commander in chief of the Polish army (1668), he distinguished himself by victories over the Cossacks and Turks. His reputation was so great that he was elected king in preference to the Habsburgs’ candidate. In 1683 he concluded a treaty with Emperor Leopold I against the Ottoman Turks. When a Turkish army approached Vienna later that year, he rushed there with troops, took command of the entire relief force, and achieved a brilliant victory, briefly restoring the kingdom of Poland-Lithuania to greatness for the last time. He was unsuccessful in a Hungarian campaign (1683–91) to liberate Moldavia and Walachia from Ottoman rule. Later rebellion within his own family, with nobles fighting each other rather than the Turks, led finally to Poland’s downfall in the 18th century.
