In 1569 was established the Polish-Lithuanian Commonwealth (a bi-confederation of Poland and Lithuania ruled by a common monarch, who was both the King of Poland and the Grand Duke of Lithuania), which became one of the largest and most populous countries of 16th- and 17th-century Europe. Due to its central location between the Commonwealth's capitals of Kraków and Vilnius, Warsaw became practically the capital of the Commonwealth in 1596, when King Sigismund III Vasa moved his court from Kraków to Warsaw (also the permanent seat of the General Sejm from the same year), although the modern concept of a single capital city was to some extent inapplicable in the feudal and decentralized Commonwealth.
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