Sigismund III, 1566–1632, king of Poland (1587–1632) and Sweden (1592–99). The son of John III of Sweden and Catherine, sister of Sigismund II of Poland, he united the Vasa and Jagiello dynasties. He was a Roman Catholic; his marriage (1592) with Anne of Hapsburg linked him with the Catholic monarchs of Europe. A period of factional strife after the death (1586) of King Stephen Báthory was ended by the election of Sigismund as king of Poland, effected through the support of Jan Zamojski, who opposed the candidacy of Maximilian of Austria. In 1592, Sigismund inherited the Swedish throne from his father, but his reluctance to accept Protestantism as the state religion in Sweden involved him in conflict with the Swedes and with his uncle, who was regent (see Charles IX). Although finally crowned in 1594, Sigismund was defeated (1598) at Stangebro and was formally deposed by the Swedish diet in 1599. He retained his claims to Sweden and after 1600 fought intermittently with his uncle and later with his nephew, Gustavus II, to whom he lost (1629) most of Livonia. Sigismund intervened in Russia, in the turmoil after the death of Boris Godunov, by sanctioning Polish support of the two pretenders who claimed to be Dmitri. Sigismund dreamed of conquering all of Russia. In 1610, taking advantage of chaos in that country, Sigismund continued his military conquest and took Moscow. His son Ladislaus was elected czar, but Sigismund desired the throne for himself. As a Catholic, he was opposed for religious as well as political reasons. In 1612 an improvised Russian army under Prince Pozharski expelled the Poles, and Michael Romanov was elected czar of Russia. Poland retained Smolensk and other border towns. Peace with Russia came only after Sigismund's death—in 1634, under Ladislaus IV, Sigismund's son and successor. Sigismund's pro-Catholic policy helped to effect the union (1596) of the Ruthenian Church in Poland-Lithuania with the Church of Rome. This period also saw the start of intermittent war with the Ottoman Empire, lasting until Poland obtained a favorable treaty in 1621. Sigismund's use of Austrian aid to limit the powers of the diet and the dissatisfaction of the Protestants led to a rebellion (1606–7) under Nicholas Zebrzydowski, the palatine of Kraków. Although the rebels were defeated, their cause triumphed; no more attempts were made to change the constitution.