The Schmalkaldic League (German: Schmalkaldischer Bund) was a defensive alliance of Lutheran princes within the Holy Roman Empire during the mid-16th century. Although originally started for religious motives soon after the start of the Protestant Reformation, its members eventually intended for the League to replace the Holy Roman Empire as their source of political allegiance. While it was not the first alliance of its kind, unlike previous formations, such as the League of Torgau, the Schmalkaldic League had a substantial military to defend its political and religious interests. It receives its name from the town of Schmalkalden, in the German province of Thuringia.

Origins and members
The members of the League agreed to provide 10,000 infantry and 2,000 cavalry

Activities

Main article: Schmalkaldic War The Schmalkaldic War
In 1548 the victorious Charles forced the Schmalkaldic League to agree to the terms set forth in the Augsburg Interim. However, by the 1550s, Protestantism had established itself too firmly within Central Europe to be ended by brute force. A small Protestant victory in 1552 forced Charles, weary from three decades of war, to sign the Peace of Passau, which granted some freedoms to Protestants and ended all of Charles' hopes at religious unity within his empire. Three years later, the Peace of Augsburg granted Lutheranism official status within the Holy Roman Empire and let princes choose the official religion within the domains they controlled.