Treaty of Mutual Cooperation and Security between the United States and Japan
The Japanese nuclear weapon program was conducted during World War II. Like the German nuclear weapons program, it suffered from an array of problems, and was ultimately unable to progress beyond the laboratory stage. Following the atomic bombings of Hiroshima and Nagasaki, World War II and the deconstruction of the imperial military, Japan came under the US "nuclear umbrella" on the condition that it will not produce nuclear weapons. This was formalized in the Security Treaty Between the United States and Japan, which preceded the current security alliance, the Treaty of Mutual Cooperation and Security between the United States and Japan.