Lombard League, an alliance formed in 1167 among the communes of Lombardy to resist Holy Roman Emperor Frederick I when he attempted to assert his imperial authority in Lombardy. Previously the communes had been divided, some favoring the emperor and others favoring the pope. However, after Frederick proclaimed his sovereignty in Italy at the Diet of Roncaglia (1158), twice invaded Italy (1158, 1166), and appointed German officials in all Lombard towns, even the imperial cities joined the coalition against him. The league was supported by Pope Alexander III, for whom its fortified city of Alessandria was named. In 1176 the league defeated Frederick at Legnano. After the peace of Constance (1183), which confirmed the freedom of the cities, the alliance tended to break again into rival factions. The league was revived in 1226 against Holy Roman Emperor Frederick II, who in 1237 defeated it at Cortenuova. The Lombard communes then ranged themselves on opposing sides in the quarrels between the popes and the Hohenstaufen.
