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Why was the Battle of Legnano a major defeat for Frederick I?

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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.

The Battle of Legnano, fought on May 29, 1176, was a major defeat for Frederick I because his imperial forces were thoroughly routed by the army of the Lombard League, which was led by Milan.12

This military failure forced Frederick to accept the reality that he could not achieve his goal of bringing the northern Italian communes under direct imperial authority through force. Consequently, the defeat compelled him to shift his strategy toward diplomacy. This led to a six-year truce and eventually the Peace of Constance in 1183. While Frederick managed to salvage some administrative rights and imperial power through these negotiations, he was ultimately forced to renounce the regalia—the royal rights and income—he had previously claimed at Roncaglia. Thus, the battle effectively ended his attempt to impose absolute control over the region.13