Through hard work and determination, he secured a place in the 2nd class of the Imperial Japanese Army Academy at the age of 20.

He was then promoted to major and ordered to develop a semi automatic pistol for the Japanese military.

Most of the pistols were produced by the Tokyo Arsenal with a smaller number manufactured by the Tokio Gasu Denky.

[8] At the end of World War II, Nambu announced that his company would cease all weapons production; however, his facilities were sequestered under the American occupation authorities and continued to produce equipment (under the name Shin-Chuō Industries) for the police and subsequently for the post-war Japanese National Safety Forces, the predecessor to the current Japanese Self-Defense Force.

Nambu died in May 1949, and his company was absorbed into the Japanese precision equipment manufacturer Minebea Co.