The three ships had limited careers during World War I, and did not see action. On the night of 2/3 August 1916, "Leonardo da Vinci" was sunk by an internal explosion. She was raised in 1919; the navy planned to repair and modernize her, but lacked sufficient funds, and she was sold in 1923. The two surviving ships were heavily rebuilt in the mid-1930s, and both saw action during World War II. On the night of 11/12 November 1940, both ships were attacked by British torpedo bombers in the Battle of Taranto. "Conte di Cavour" was badly damaged, and had not been fully repaired when Italy surrendered in September 1943. "Giulio Cesare" meanwhile escaped unscathed, and participated in the battles of Cape Spartivento and First Sirte in November 1940 and December 1941, respectively. After the end of the war, "Conte di Cavour" was scrapped, and "Giulio Cesare" was surrendered to the Soviet Union. Renamed "Novorossiysk", she was ultimately sunk in October 1955 by an old German mine left over from World War II. Her wreck was later salvaged in 1957 and broken up thereafter.