Frederick I Barbarossa, was emperor of the Holy Roman Empire, King of Germany (1152-1190), King of Italy (1155-1190) and, with the name of Frederick III, Duke of Swabia (1147-1152 and 1167-1168) . Son of Frederick II of Hohenstaufen, duke of Swabia, and grandson of Conrad III of Germany, he was named by the latter as a successor to the German princes.
When Corrado died (1152) Barbarossa became king of Germany and emperor of the Holy Roman Empire. In exchange for the support received in the election, Federico assigned Bavaria to his cousin Enrico il Leone. But that gesture was in fact the first step in a policy of pacification of the German area, which led to the strengthening of the great secular and ecclesiastical nobility. The source of recurrent conflicts was the imperial policy in Italy, where the municipalities had usurped some rights and no longer recognized the authority of imperial officials.
After having restored the order with the destruction of Tortona, Federico received the crown of King of Italy in Monza (1155). Then he went down to Rome, where he suffocated the autonomist uprising led by Arnaldo da Brescia; Once the city was restored to Pope Adrian IV, he was crowned emperor. In 1158 he returned to Italy to reaffirm his rights over the Lombard Municipalities, including the power to appoint the mayor of each city. Milan, Cremona, Bergamo and Mantova considered this request irreconcilable with the communal freedoms recognized by previous emperors and firmly opposed it: it was the beginning of a long series of battles, which lasted until 1183 (the year in which peace was signed di Costanza) and that counted five descents of the emperor in Italy. The excessive interference of Barbarossa in papal matters led to a serious rift between the church and the empire, which resulted in open hostility to the death of Hadrian IV (1159). Federico did not recognize the legitimacy of the new pontiff Alexander III and appointed a series of antipopes. The Pope reacted by holding an anti-imperial alliance with the Municipalities, to which the Kingdom of Sicily and Venice adhered.
In 1162 Barbarossa led a ruthless campaign against Milan, Crema and their allies, and razed the two cities to the ground. Between 1167 and 1168 he occupied Rome and installed an antipope on the papal throne, Pasquale III. In response, Alexander III, a refugee in France, excommunicated him. Meanwhile, with the oath of Pontida was established the Lega Lombarda (April 7, 1167), formed by the cities of Milan, Cremona, Mantua and Bergamo, which were later joined by many other municipalities of northern Italy, under the protection of the Pope. Over the next seven years the League strengthened militarily, rebuilt Milan, founded the stronghold of Alexandria and organized a federal administration system. The fifth descent of Federico in Italy (1174-1176) ended with his defeat by the army of the League led by Alberto da Giussano (battle of Legnano, May 1176).
In 1177 Frederick was forced to recognize Pope Alexander III and in 1183 he signed the peace of Constance, on the basis of which he had to grant autonomy to the Lombard Municipalities, while retaining limited authority over the investiture of the main municipal offices. After the campaign in Italy, Federico committed himself to increase his power in Central Europe: he forced Poland to pay a tribute to the empire, raised Bohemia to the kingdom and transformed the margraviate of Austria into an independent hereditary duchy.
In 1180 he succeeded in ending the fight against the Guelphs (supporters of the house of Bavaria), repressing the revolt led by his cousin, the Guelph Henry the Lion, and depriving the latter of almost all his possessions. In 1186 he combined the marriage between his son Henry and Constance d'Altavilla, heir to the Kingdom of Sicily, under which the Hohenstaufen dominated the Mediterranean area; to this end, Frederick also finalized his participation in the third crusade, during which he died while swimming in the river Göksu, in present-day Turkey.