active until 30 August 1945, when, in Japanese waters, this last Fascist Italian submarine shot down a North American B-25 Mitchell bomber of the United States Army Air Forces. After World War II After the end of hostilities, the Regia Marina started a long and complex rebuilding process. At the beginning of the war, the Regia Marina was the fourth largest navy in the world with a mix of modernised and new battleships. The important combat contributions of the Italian naval forces after the signing of the armistice with the Allies on 8 September 1943 and the subsequent cooperation agreement on 23 September 1943 left the Regia Marina in a poor condition. Much of its infrastructure and bases were unusable and its ports mined and blocked by sunken ships. However, a large number of its naval units had survived the war, albeit in a low efficiency state. This was due to the conflict and the age of many vessels. The vessels that remained were: 2 incomplete and damaged aircraft carriers 5 battleships 9 cruisers 11 destroyers 22 frigates 19 corvettes 44 fast coastal patrol units 50 minesweepers 16 amphibious operations vessels 2 school ships 1 support ship and plane transport various submarine units On 2 June 1946, the Italian monarchy was abolished by a popular referendum. The Kingdom of Italy (Regno d'Italia) ended and was replaced by the Italian Republic (Repubblica Italiana). The Regia Marina became the Navy of the Italian Republic (Marina Militare). Peace treaty On 10 February 1947, a peace treaty was signed in Paris between the Italian Republic and the victorious powers of World War II. The treaty was onerous for the Italian Navy. Apart from territorial and material losses, the following restrictions were imposed: A ban on owning, building or experimenting with atomic weapons, self-propulsion projectiles or related launchers A ban on owning battleships, aircraft carriers, submarines and amphibious assault units. A ban on operating military installations on the islands of Pantelleria and Pianosa; and the Pelagie Islands. The total displacement, battleships excluded, of the future navy was not allowed to be greater than 67,500 tons, while the staff was capped at 25,000 men. The treaty also ordered Italy to put the following ships at the disposals of the victorious nations United States, Soviet Union, Great Britain, France, Greece, Yugoslavia, and Albania as war compensation: 3 battleships: , , ; 5 cruisers: , , , and