During the interregnum that followed Ottavio again tried to induce the governor of Parma to give up the city to him, but met with no better success; however, on the election of Giovan Maria Ciocchi (Julius III.) the duchy was conferred on him (1551).
The disobedience of his favourite Ottavio hastened the death of the old pope (Nov.
As an adherent of the emperor he suffered in consequence of imperial reverses, and was forced to confirm Parma to Ottavio Farnese, the ally of France (1552).
But in 1549 Pier Luigi was assassinated by his outraged subjects, and the emperor thereupon claimed the two duchies for his son-in-law Ottavio Farnese, Paul's grandson.