As a young man, he fought in the service of Henry II of France, fighting against the Habsburgs. Soon after his accession to the throne, he was forced by Pope Pius IV to send back his mother to France, due to her Calvinist creed. He commanded Ferrara at the time of the 1570 Ferrara earthquake.
In 1583 he allied with Emperor Rudolf II in the war against the Turks in Hungary.