[1][2] In 1920 he was executive officer on the protected cruiser Etna, on an international mission to Novorossijsk on the Black Sea, and distinguished himself during the tumultuous departure of the ship under the fire of Soviet artillery, earning his first Silver Medal of Military Valor.

[1][2] After promotion to captain, he was in command of the heavy cruisers Fiume and Zara and held important positions abroad, including that of Naval Attaché in Paris between 1935 and 1937 and, upon returning to Italy, between from 1937 to 1939, the post of chief of staff of the 1st Fleet.

[1][2] When Italy entered World War II Ferreri was assigned to Supermarina at the Merchant Traffic Protection Office, and in November 1940 he was promoted to rear admiral.

In January 1942 he became Chief of Staff of the Commander-in-Chief of the Naval Battle Forces, a position he held, after promotion to vice admiral in July 1942, until May 1943, when he was transferred to the Supreme Command to assume the direction of the Traffic Office.

During this long period Ferreri devoted all his energies to the reorganization of the Italian Navy, decimated by war losses and by the clauses of the Paris Peace Treaty, laying the foundations for the subsequent renovation and reconstruction work that would be continued by his successors.