army commander and political activist notable in Polish affairs.

As a young army commander, Tarnowski defeated the army of the Moldavian prince Bogdan in southeastern Poland (1509) and took a leading part in victories over the Tatars at Wiśniowiec in 1512 and the Muscovites at Orsza in 1514. After travelling through western Europe and the Middle East (1517–19), he was entrusted with the command of a Portuguese army that he led to victory against the Moors (1520). Returning to Poland (1521), he led Polish forces in Prussia against the Teutonic Knights. Appointed commander in chief of the army (1527) by King Sigismund I the Old, he halted the Tatar raids into Poland, defeated the Moldavians at Obertyn in August 1531, and directed a campaign against the Muscovites in 1535. Appointed governor of Kraków province (1535) in recognition of his military services, he encouraged new settlements in southeastern Poland.

As a member of the Polish senate, Tarnowski supported Sigismund I during the “Poultry War,” a revolt (1536) by the szlachta (gentry) against the king's attempt to increase his power. In 1547 he sided with King Sigismund II Augustus when the szlachta tried to force an annulment of the king's marriage to Barbara Radziwiłł. But in 1553, though a Catholic, Tarnowski supported the largely Calvinist szlachta against the restoration of independent Roman Catholic ecclesiastical courts. He wrote De bello cum…Turcis gerendo (1552; “Concerning the Wars with the Turks”), about the emperor Charles V's projected war against the Turks, and Consilium rationis bellicae (1558; “Plans on Methods of War”), on traditional Polish methods of warfare.