The Amagi class battlecruisers were ordered in the 1919 Program (Akagi and Amagi) and 1920 Program (Atago and Takao). These were to be a part of the 8-8 Project (8 battleships / 8 battlecruisers).
The Amagi class was designed by Y. Hiraga in 1919.
Due to the agreement in the Washington Treaty the Amagi class ships had to be cancelled. The Atago and Takao were broken up while still on the stocks.
The Amagi and Akagi were to be converted into aircraft carriers.