their careers. Both ships had their 100 mm guns replaced with newer Mod 31 versions of the same caliber. In 1937–1938, the two aft-most 100 mm guns were removed, along with all four 12.7 mm machine guns; eight 54-cal. Breda M1932 guns and eight Breda M1931 machine guns, all in twin mounts, were installed in their place. In 1942, Trento received four 65-cal. Breda M1940 guns in single mounts, with Trieste receiving eight of those guns the following year. Both vessels were protected with an armored citadel that covered the ships' vitals, including the machinery spaces and ammunition magazines. The vertical armor belt was thick and ran from forward of the fore main battery turrets to aft of the rear turrets. Either end of the belt was capped with armored bulkheads thick on the upper portion; the forward bulkhead had a lower section that was reduced to , and the aft bulkhead's lower portion was reduced to . Their armor deck was 50 mm thick in the central portion of the ship and reduced to aft, with thick sloped sides. The armor deck did not extend forward of the citadel. The gun turrets had thick plating on the faces and the supporting barbettes they sat in were 70 mm thick above the armor deck and 60 mm thick below. The main conning tower had 100 mm thick sides and a 50 mm thick roof; above the tower was a fire control director with thick sides and a 60 mm thick roof. Ships Service history Trento and Trieste were named for the two largest unredeemed cities taken from Austria-Hungary in the aftermath of World War I. They frequently served as the flagship of the Cruiser Division throughout the 1930s. During the pre-war period, Trento made lengthy trips abroad, including a tour of South America from May to October 1929 and a deployment to China from January to June 1932 to protect Italian nationals during the Chinese Civil War. Both vessels took part in numerous naval reviews held for visiting foreign leaders in the 1930s, including Adolf Hitler of Nazi Germany and Miklós Horthy, the Regent of Hungary. In 1938 Trieste helped transport soldiers of the Corpo Truppe Volontarie (Corps of Volunteer Troops), which had been sent to Spain to fight in the Spanish Civil War, back to Italy. After Italy entered World War II in June 1940, Trento and Trieste saw