Throughout his life, Leonardo reached high honors and positions in service to the papacy, the Holy Roman Empire and the Kingdom of Naples.

He served as the captain of the cavalrymen of the papal guard, an Imperial Counsellor of State in the Holy Roman Empire and a field marshal and vicar general in the Kingdom of Naples.

In the Holy Roman Empire, Emperor Charles VI (r. 1711–1740) made Leonardo the Imperial Counsellor of State on 6 October 1725.

On 23 April 1732, he was made field marshal and vicar general of the Principato Ultra [it], one of the kingdom's administrative divisions.

[5] On 16 January 1724, Leonardo married Camilla Cantelmo Stuart (or Stuard), princess of Pettora and duchess of Popoli.