The Schmalkaldic League (English: /ʃmɔːlˈkɔːldɪk/; German: Schmalkaldischer Bund; Medieval Latin: Foedus Smalcaldicum or Liga Smalcaldica) was a military alliance of Lutheran principalities and cities within the Holy Roman Empire during the mid-16th century.

[1] Although created for religious motives soon after the start of the Reformation, its members later came to have the intention that the League would replace the Holy Roman Empire as their focus of political allegiance.

The League was officially established on 27 February[3] 1531 by Philip I, Landgrave of Hesse, and John Frederick I, Elector of Saxony, the two most powerful Protestant rulers in the Holy Roman Empire at the time.

[5]The formation of the Schmalkaldic League in 1531 and the threatening attitude of Sultan Suleiman the Magnificent, who, in April 1532, assumed the offensive with an army of 300,000 men, caused Ferdinand of Austria to grant the religious peace.

[6] Those who supported the Reformation obtained religious liberty until the meeting of a council and in a separate compact all proceedings in matters of religion pending before the imperial chamber court were temporarily paused.

They rarely provoked Charles directly but confiscated church land, expelled bishops and Catholic princes and helped spread Lutheranism throughout northern Germany.

The tactical support ended in 1544 with the signing of the Treaty of Crépy in which the French king, who was fighting the Emperor in Italy, pledged to stop backing the Protestant princes and the League in Germany.

[12] After the peace with France, Charles signed the Truce of Adrianople in 1547 with the Ottoman Empire, which was allied to Francis, to free even more Habsburg resources for a final confrontation with the League.