SIGISMUND II. (152o-1572), king of Poland, was the only son of Sigismund I. (q.v.), whom he succeeded in 1548, and Bona Sforza. At his first diet (Oct. 31, 1548), he came into con flict with the szlachta, now becoming powerful, who, secretly supported by the Austrian court and the queen-mother, threat ened to renounce their allegiance unless he repudiated his second wife, the beautiful Lithuanian Calvinist, Barbara Radziwill, daugh ter of the famous Black Radziwill. But his firm refusal produced a reaction, and at the second diet (155o) the szlachta was less turbulent. On the death of Barbara, under suspicious circum stances, five days after her coronation (Dec. 7, 155o) Sigismund made a purely political marriage with the Austrian archduchess Catherine, sister of his first wife Elizabeth, who had died young. Catherine proving childless, Sigismund, being the last male of the Jagiellos in the direct line, was anxious to have an heir, and the diet had undertaken to legitimize and acknowledge any fruit of his liaisons with Barbara Gizanka and Anne Zajanczkowska; but the Habsburgs, who coveted the throne, successfully opposed the wish of the Protestant party, that he should divorce Catherine and remarry. Actually he survived the queen's death (Feb. 28,
1572) barely six months and died childless. Sigismund's reign was a period of internal turmoil and external expansion. He saw the invasion of Poland by the Reformation, the democratic upheaval which placed all political power in the hands of the szlachta; the collapse of the ancient order of the Knights of the Sword in the north (which led to the acquisition of Livonia by the republic) ; and the consolidation of the Turkish power in the south. Sigismund's most striking and personal achievement was the union of Lublin, which made of Poland and Lithuania one body politic; and put an end to the jealousies and discords of centuries. (See POLAND : History.) He died at Knyszyne on July 6, 1572.