Gaining experience and maturity in the tactics of guerrilla warfare, he took part (with the Lombard volunteers) in the "Legione Manara" in the Brescian and Trentine campaigns of the First Italian War of Independence, and participated in the formation of the Roman Republic, in 1849. During the battle against the French, which finally freed Rome from the insurgents, Dandolo fought at the rank of captain in the "Battaglione Bersaglieri Lombardi", under the command of Luciano Manara.