Updated: August 2012

At the dawn of the nuclear age, the United States hoped to maintain a monopoly on its new weapon, but the secrets for making nuclear weapons soon spread. Four years after the United States dropped atomic bombs on Japan in August 1945, the Soviet Union detonated its first nuclear device. The United Kingdom (1952), France (1960), and China (1964) followed. Seeking to prevent the nuclear weapon ranks from expanding further, the United States and other like-minded states negotiated the nuclear Nonproliferation Treaty (NPT) in 1968. In the decades since, several states have abandoned nuclear weapons programs, but others have defied the NPT. India, Israel, and Pakistan have never signed the treaty and possess nuclear arsenals. Iraq initiated a secret nuclear program under Saddam Hussein before the 1991 Persian Gulf War. North Korea announced its withdrawal from the NPT in January 2003 and has tested nuclear devices since that time. Iran and Libya have pursued secret nuclear activities in violation of the treaty’s terms, and Syria is suspected of doing the same. Still, nuclear nonproliferation successes outnumber failures and dire forecasts decades ago that the world would be home to dozens of states armed with nuclear weapons have not come to pass.