1st Naval Armaments Supplement Programme

IJN cruisers Mogami, Mikuma, Kumano all constructed under the "Circle One" plan

The 1st Naval Armaments Supplement Programme (マル1計画, 第一次補充計画, Maru 1 Keikaku, Dai-Ichi-Ji Hojū Keikaku), otherwise known as the "Circle One" plan was the first of four expansion plans of the Imperial Japanese Navy between 1930 and the start of World War II.