Always with his fierce cousin, he commanded the Florentine artillery in the war for Siena in 1554; the next summer he assaulted and overcame Porto Ercole fortress after a four-day artillery barrage, then with 700 German Landsknechts he defended Populonia against a Turkish sea-borne assault, receiving support from the Florentine cavalry.
He was always by his fierce cousin's side as he led the Florentine artillery during the war for Siena in 1554. The following summer, he successfully captured Porto Ercole fortress after a four-day bombardment, then defended Populonia against a Turkish naval attack with the help of German Landsknechts and Florentine cavalry.