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What happened at the Battle of Legnano in 1176?

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Medieval manuscript miniature showing Frederick I as a crowned crusader holding an orb and scepter, with Henry of Schaftlarn kneeling and presenting a book to him. — Frederick I Frederick I as a Crusader with (right) Henry of Schäftlarn dedicating to him a copy of the *History of the First Crusade* by Robert of St. Remy; miniature from a manuscript in the Vatican Library.

At the Battle of Legnano on May 29, 1176, the forces of the Lombard League—a coalition of northern Italian cities led by Milan—engaged in a pitched battle against the army of the Holy Roman emperor Frederick I Barbarossa.123

The imperial supporters were decisively routed by the league's forces. This military defeat forced Frederick to accept the reality of his weakened position in Italy, leading him to pursue a diplomatic campaign that resulted in a six-year truce with the Lombard communes and the recognition of Pope Alexander III. This conflict ultimately paved the way for the Peace of Constance in 1183, in which Frederick renounced certain imperial claims while preserving key administrative rights, allowing him to salvage a portion of his authority.241