Japan is the only country to have suffered nuclear attacks in history. Thus in 1967, Prime Minister Eisaku Satō outlined the Three Non-Nuclear Principles by which Japan stands against the production or possession of nuclear weaponry. However, due to its high technology level and large number of operating nuclear power plants, Japan is considered to be "nuclear capable", i.e., it could develop usable nuclear weapons within one year if the political situation changed significantly. Thus many analysts consider Japan a "de facto" nuclear state. Numerous politicians such as Shinzo Abe and Yasuo Fukuda explained that Japan's constitution doesn't ban possession of nuclear weapons. They should be kept at a minimum and used as tactical weapons. The 1951 US-Japan Security Treaty puts Japan under the US nuclear umbrella.