The article analyzes the role of sieges during the war between emperor Frederick II of Swabia and the Italian communes led by Milan (1239-1250). The emperor besieged five big cities: Brescia (1238), Milan (1239), Faenza (1240-41), Viterbo (1243) e Parma (1247-48), but only Faenza surrendered. The paper discusses the military, political and social reasons of the failures of imperial forces.
Keywords: Italian communes, Emperor Fredrick II, Sieges, Medieval war.