The were ordered during the early 1920s. They were larger versions of the preceding "Nagato" class, and carried an additional twin-gun 41 cm turret. Both ships were launched in late 1921, but the first ship, , was cancelled in accordance with the terms of the Washington Naval Treaty before she could be completed, and was used in experiments testing the effectiveness of its armor scheme before being scuttled. The hull of the second ship, , was converted into an aircraft carrier to replace an that had been wrecked by the Great Kanto earthquake of 1923. The carrier supported Japanese troops in China during the Second Sino-Japanese War and took part in the attack on Pearl Harbor and the invasion of Rabaul in the Southwest Pacific in January 1942. The following month her aircraft participated in a combined carrier airstrike on Darwin, Australia, during the Dutch East Indies campaign. She was sunk during the Battle of Midway in 1942.