Nakajima received financial support from fellow engineer Seibei Kawanishi, and the company was called Nihon Hikoki Seisakusho KK (Japanese Aeroplane Manufacturing Work Co. Ltd).

He turned control of Nakajima Aircraft over to his brother in 1931 in order to devote his efforts to politics full-time, and was subsequently re-elected four times from the Gunma No.

Nakajima was highly critical of the decision by Japan to declare war on the United States, and warned of the dangers posed by America’s industrial strength and production capabilities and growing air power.

He was outraged by the decision of the Japanese military to abandon his project for a long-range bomber capable of striking at targets in North America.

Afterwards, he was arrested along with all other members of the former Japanese government by the Supreme Commander of the Allied Powers and was held in Sugamo Prison for trial for war crimes.