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The bomb, the brink and the reactor: eighty years of the atom

THE ATOM, FROM TRINITY TO THE EDGE

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In eighty years the atom went from one test in the New Mexico desert to about 70,000 warheads, and back down to about 12,000, with no binding treaty left to limit them. Here is the escalation, the near misses, the reactors that failed, and where it stands in 2026.

1945: the first three — THE RECORD · ESTIMATED

The first atomic bomb was tested at Trinity, New Mexico, on 16 July 1945. On 6 August a uranium bomb destroyed Hiroshima, and on 9 August a plutonium bomb destroyed Nagasaki. By the end of 1945 about 140,000 people had died in Hiroshima and about 74,000 in Nagasaki, by the two cities' own estimates. They are the only nuclear weapons ever used in war.

1949 to 1961: the climb — THE RECORD · MEASURED

The Soviet Union tested its first bomb on 29 August 1949. The United States tested the first hydrogen bomb, Ivy Mike, on 1 November 1952: 10.4 megatons, about 700 times the Hiroshima bomb. On 1 March 1954 the Castle Bravo test ran to 15 megatons, far past its design, and its fallout fell on Marshall Islanders and on a Japanese fishing boat, the Lucky Dragon No. 5. On 30 October 1961 the Soviet Union exploded the largest bomb ever, the Tsar Bomba, about 50 megatons.

October 1962: the brink — THE RECORD

For thirteen days in October 1962 the United States and the Soviet Union stood at the edge of nuclear war over Soviet missiles in Cuba. It ended with the missiles withdrawn, and a US pledge, kept secret at the time, to remove its missiles from Turkey. A hotline between Washington and Moscow followed in 1963, and the Partial Test Ban Treaty banned tests in the air, in space and under water for the states that joined it; France and China, which did not, went on testing in the air until 1974 and 1980.

1968 to 1986: the count climbs anyway — THE RECORD · ESTIMATED (FAS)

The Non-Proliferation Treaty (signed 1968, in force 1970) kept the bomb, by law, to the five states that had it. It did not stop the count: the world's stockpile peaked in 1986 at about 70,000 warheads, by the Federation of American Scientists' estimate. On 26 September 1983 a Soviet early-warning system reported US missiles in flight. The officer on duty judged it a false alarm. It was one.

The reactors — THE RECORD · THE LONG-TERM TOLLS: CONTESTED

On 28 March 1979 a reactor at Three Mile Island, Pennsylvania, partly melted down. The US Nuclear Regulatory Commission found the radiation released too small to cause any detectable health effect. No new US reactor had been ordered since 1978, and licences for new ones resumed only in 2012. On 26 April 1986 reactor 4 at Chernobyl, in Soviet Ukraine, exploded and burned. Two workers died that night and 28 more of radiation sickness within months; more than 330,000 people were moved from their homes, and a zone of about 2,600 square kilometres is still closed. How many will die of it in the end is contested: the UN's agencies projected up to 4,000 among the most exposed, and other studies put it far higher. On 11 March 2011 an earthquake and tsunami led to three meltdowns at Fukushima Daiichi, Japan, and more than 150,000 people were evacuated. Japan attributes one worker's death to the radiation, and more than 2,000 deaths in the prefecture to the evacuation itself.

2026: no binding limit — THE RECORD · ESTIMATED (FAS)

New START, the last treaty limiting US and Russian deployed strategic warheads, to 1,550 each, expired on 5 February 2026. For the first time in decades no legally binding limit is left on the two largest arsenals. Russia has said it will keep to the old limits as long as the United States does; the United States has not agreed. Nine states hold about 12,187 warheads, by the Federation of American Scientists' 2026 estimate. On 27 January 2026 the Bulletin of the Atomic Scientists set its Doomsday Clock at 85 seconds to midnight, the closest in its history.

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