The United States holds the second largest arsenal of nuclear weapons among the nine nuclear-armed countries. Under the Manhattan Project, the United States became the first country to manufacture nuclear weapons and remains the only country to have used them in combat, with the bombings of Hiroshima and Nagasaki in World War II against Japan. In total it conducted 1,054 nuclear tests, the most of any country. It is an original party to and one of the five "nuclear-weapon states" recognized by the 1968 Treaty on the Non-Proliferation of Nuclear Weapons.
, the US and Russia possess a comparable number of warheads; together more than 90% of the world's stockpile. The US holds in total 5,177 warheads, of which 3,700 are stockpiled, and 1,477 are awaiting dismantlement. Of the stockpile, 1,770 are deployed, while 1,930 are held in reserve. The president of the United States has the sole authority to use nuclear weapons. US policy permits nuclear first use, and aims to "deter Russia, the PRC, and the DPRK simultaneously".
The US stockpile is mostly under Strategic Command, assigned to its nuclear triad: 1,920