Cantelmo, son of the duke of Popoli and of Laura d'Evoli, was born in Pettorano sul Gizio on 2 August 1598.

He remained in Italy to serve in the initial stages of the War of the Mantuan Succession, taking part in the Siege of Casale.

As general of artillery he played an important role in the Habsburg victory in the Battle of Kallo (1638).

He was interested in history and politics, and wrote on the art of war, but his writings have not been preserved.

[1] By 1644 he was in Spain, where he was appointed a member of the Council of War and given command of the Army of Catalonia as acting captain general (substituting for Felipe de Silva).