Battle of Desio The Battle of Desio was fought on 21 January 1277 between the Della Torre and Visconti families for the control of Milan and its countryside . The battlefield was located near the modern Desio , a commune outside the city in Lombardy , northern Italy . Although generally considered one of the numerous minor battles fought in the 13th century in Italy during the Wars of the Guelphs and Ghibellines , it was in fact the conclusion of a long inner struggle for the possession of Milan , leading to the transformation of the former democratic regime into an aristocratic signoria . The Visconti victory granted them the rule over Milan , which lasted until the 15th century . Background . In the 13th century , the politic life in Milan shared the same path of many other communes in Italy , living an increasing series of inner divisions and episodes of corruption . In the decades preceding the battle , the noble family of the Della Torre ( or Torriani ) had gained the most important political charges in the commune , this way nullifying the democratic ideals of the original medieval commune . They had also launched a program of public works and military expansions , which however brought the Milanese treasure to collapse ; the use of often reckless mercenary units further esacerbated the population , granting an increasing support for the Della Torre traditional enemies , the Visconti . On 22 July 1262 Ottone Visconti was created archbishop of Milan by Pope Urban IV , against the Della Torre candidate , Raimondo della Torre , bishop of Como . The latter thus started to publicize an alleged Visconti ' s nearness to the heretic Cathars and charged them of high treason : the Visconti , who accused the Della Torre of the same crimes , were then banned from Milan and their properties confiscated . The civil war which ensued caused more damage to Milan ' s population and economy , lasting for more than a decade . The battle . The Milanese had destroyed most of the fortifications in the towns of Brianza north to the city , fearing the could be used as strongpoints by the rebels and their northern ally , Como . They had however spared those of Desio , some 30 km north to Milan , as there converged three important trade routes from Como , Erba and Lecco . On 20 January 500 Milanese heavy cavalry moved to occupy Desio , where they would be joined by other 500 heavy cavalry which had just pushed back a rebel attack at Civate , and by some 400 infantry . Likely , their strategy was to attack Visconti ' s vanguard army , which amounted to some 1 , 200 men ( most infantry and archers ) , easily defeating it . Next step was the destruction of the rebel base of Como . However , during the inhabitants of Desio abandoned the now hated Milanese government . Visconti ( whom , according to tradition , was warned of the occasion ; while others state that the Visconti attack pushed the populace to rebellion ) rushed to the town before the Milanese reinforces could arrive . Whether Visconti had foreknowledge , or the villagers rebelled , the fact is that at dawn on January 21 , 1277 , the surprise attack against the government forces succeeded and the village of Desio was captured . The gates were opened , and the rebels defeated the Milanese army : Francesco della Torre was killed , while his brother Napo , lord of Milan , was jailed in the Castel Baradello at Como , where he died the following year . Despite the minor size of the battle , Napo ' s capture was a fatal blow for the della Torre ' s party . The Visconti easily seized Milan and put their supporters in the most important positions , gradually strengthening their power , which lasted until the mid - 15th century .