His well-placed father, a Piedmontese general, bestowed kinship ties that led to young Cagni being accepted for training by the Italian navy as a future officer.
Organizing a group of 20 Italian and Norwegian men led by himself, the royal duke sailed on 12 June 1899 from Christiania for the recently discovered Franz Josef Land, via Archangel'sk.
Luigi Amedeo deputized command over the lead dogsled party to Cagni, who forged northward from Franz Josef Land on 11 March.
Throwing away almost all of their remaining impedimenta and crowding into a single tent, the foursome regained Franz Josef Land on 23 June, twelve days after their projected survival deadline.
He led naval relief efforts in the 1908 Messina earthquake, participated in the colonial conquest of Libya in 1911–1912, served in World War I, retired in 1923 as an admiral, and was named to the Italian Senate.