Nuclear disarmament groups include the Campaign for Nuclear Disarmament, Peace Action, Greenpeace, Soka Gakkai International, International Physicians for the Prevention of Nuclear War, Mayors for Peace, Global Zero, the International Campaign to Abolish Nuclear Weapons, and the Nuclear Age Peace Foundation. There have been many large anti-nuclear demonstrations and protests. On June 12, 1982, one million people demonstrated in New York City's Central Park against nuclear weapons and for an end to the cold war arms race. It was the largest anti-nuclear protest and the largest political demonstration in American history.
In recent years, some U.S. elder statesmen have also advocated nuclear disarmament. Sam Nunn, William Perry, Henry Kissinger, and George Shultz have called upon governments to embrace the vision of a world free of nuclear weapons, and in various op-ed columns have proposed an ambitious program of urgent steps to that end. The four have created the Nuclear Security Project to advance this agenda. Organisations such as Global Zero, an international non-partisan group of 300 world leaders dedicated to achieving nuclear disarmament, have also been established.
In 1945 in the New Mexico desert, American scientists conducted "Trinity," the first nuclear weapons test, marking the beginning of the atomic age. Even before the Trinity test, national leaders debated the impact of nuclear weapons on domestic and foreign policy. Also involved in the debate about nuclear weapons policy was the scientific community, through professional associations such as the Federation of Atomic Scientists and the Pugwash Conference on Science and World Affairs.
On August 6, 1945, towards the end of World War II, the "Little Boy" device was detonated over the Japanese city of Hiroshima. Exploding with a yield equivalent to 12,500 tonnes of TNT, the blast and thermal wave of the bomb destroyed nearly 50,000 buildings (including the headquarters of the 2nd General Army and Fifth Division) and killed 70,000–80,000 people outright, with total deaths being around 90,000–146,000. Detonation of the "Fat Man" device exploded over the Japanese city of Nagasaki three days later on 9 August 1945, destroying 60% of the city and killing 35,000–40,000 people outright, though up to 40,000 additional deaths may have occurred over some time after that. Subsequently, the world’s nuclear weapons stockpiles grew.
Operation Crossroads was a series of nuclear weapon tests conducted by the United States at Bikini Atoll in the Pacific Ocean in the summer of 1946. Its purpose was to test the effect of nuclear weapons on naval ships. Pressure to cancel Operation Crossroads came from scientists and diplomats. Manhattan Project scientists argued that further nuclear testing was unnecessary and environmentally dangerous. A Los Alamos study warned "the water near a recent surface explosion will be a 'witch's brew' of radioactivity". To prepare the atoll for the nuclear tests, Bikini's native residents were evicted from their homes and resettled on smaller, uninhabited islands where they were unable to sustain themselves.
Radioactive fallout from nuclear weapons testing was first drawn to public attention in 1954 when a hydrogen bomb test in the Pacific contaminated the crew of the Japanese fishing boat Lucky Dragon. One of the fishermen died in Japan seven months later. The incident caused widespread concern around the world and "provided a decisive impetus for the emergence of the anti-nuclear weapons movement in many countries". The anti-nuclear weapons movement grew rapidly because for many people the atomic bomb "encapsulated the very worst direction in which society was moving".