dominant partner in the union.

The Polish–Lithuanian Commonwealth was marked by high levels of ethnic diversity and by relative religious tolerance, guaranteed by the Warsaw Confederation Act 1573; however, the degree of religious freedom varied over time. The Constitution of 1791 acknowledged Catholicism as the "dominant religion", unlike the Warsaw Confederation, but freedom of religion was still granted with it.

After several decades of prosperity, it entered a period of protracted political, military and economic decline. Its growing weakness led to its partitioning among its neighbors (Austria, Prussia and the Russian Empire) during the late 18th century. Shortly before its demise, the Commonwealth adopted a massive reform effort and enacted the May 3 Constitutionthe first codified constitution in modern European history and the second in modern world history (after theStefan Batory (1576–86), the kings of foreign origin were inclined to subordinate the interests of the Commonwealth to those of their own country and ruling house. This was especially visible in the policies and actions of the first two elected kings from the Swedish House of Vasa, whose politics brought the Commonwealth into conflict with Sweden, culminating in the war known as The Deluge (1655), one of the events that mark the end of the Commonwealth's Golden Age and the beginning of the Commonwealth's decline.

The Zebrzydowski rebellion (1606–1607) marked a substantial increase in the power of the Polish magnates, and the transformation of szlachta democracy into magnate oligarchy. The Commonwealth's political system was vulnerable to outside interference, as Sejm deputies bribed by foreign powers might use their liberum