The Ibuki was to be the start of a new heavy class of cruiser based on the Mogami class. Two ships were ordered under the 1941 Program.
After being launched construction was halted. Then it was decided to make the Ibuki into a fast oiler. Then in the summer of 1943 the decision was made to make the Ibuki into an aircraft carrier.
After the heavy losses at Midway the 301 had its construction halted and in its place was to be built the aircraft carrier Amagi.
There were to be two catapults for launching aircraft.