Barbarossa's army destroyed by disease in Rome

August 1, 1167

Fresh from capturing Rome, Barbarossa's forces were struck by what was probably malaria. Within days hundreds were dead, including his chancellor, his Welf cousin, and most of his German captains. The emperor fled north in disguise through hostile Lombardy and barely got home. The catastrophe broke the back of Barbarossa's fourth Italian expedition and demonstrated that Rome's notorious summer fevers were a more effective defender than any army.