Battle of Legnano

Frederick sought to rule the rich cities of northern Italy through imperial officials, as the Diet of Roncaglia (1158) had laid down. Milan resisted; it surrendered on 6 March 1162, and three weeks later much of it was destroyed on his orders. When Frederick recognized the antipope Victor IV, Pope Alexander III excommunicated him, and in 1167 the cities formed the Lombard League with the pope's backing — according to a tradition first recorded in 1505, its oath was sworn at Pontida on 7 April 1167 — and named a new city, Alessandria, in his honour. Frederick besieged Alessandria in vain from October 1174 to April 1175, and peace talks broke down. In May 1176, on his fifth Italian expedition, he was trying to get from Como to Pavia, where more imperial and Italian troops awaited him, when the League's army barred his way.

The first clash, between Borsano and Busto Arsizio, went to the imperial knights, who drove off the League's cavalry. They then charged the Milanese infantry, drawn up in successive lines with shields and long spears around the carroccio. The cavalry that had fled regrouped and returned, and the tide turned: Frederick's horse went down, the imperial standard was lost and the emperor disappeared from view, so that for some time he was believed dead. The retreat became a rout in which many imperial soldiers were killed, captured or drowned trying to cross the Ticino.

Frederick survived, and Legnano did not destroy imperial power in Italy, but it forced him to negotiate: in the Peace of Venice (1177) he recognized Alexander III, ending the schism, and gave the cities a six-year truce, and in the Peace of Constance (1183) the League acknowledged him as sovereign while keeping its communal liberties. Historians stress that the victory came from numbers, formation, terrain and the return of the League's horsemen, not from any sudden supremacy of foot soldiers over knights. Alberto da Giussano and the "Company of Death" said to have guarded the carroccio first appear in the 14th-century Milanese chronicler Galvano Fiamma. In the Risorgimento the battle became a national symbol: Verdi's opera La battaglia di Legnano was first performed in Rome in 1849, and Legnano is the only city besides Rome named in the Italian national anthem.