ON NOVEMBER 1, 1952, ON the island of Elugelab in Eniwetok Atoll in the Pacific, the U.S. Atomic Energy Commission detonated the world’s first thermonuclear explosion. Within seconds of ignition, there appeared a fireball three miles across, which slowly turned into a hundred-mile canopy of smoke. Elugelab was obliterated, replaced by a huge crater in the ocean floor.

Even to jaded weapons designers, this was something new. The bomb dropped on Hiroshima in 1945 had killed 80,000 people, disfigured tens of thousands more, and destroyed untold amounts of property. This device was 1,000 times as powerful. One scientist who witnessed the test recalled it as being “so huge, so brutal—as if things had gone too far.”

The idea of a thermonuclear, or hydrogen, bomb had been conceived of as early as 1941, but it was shelved during World War II, when the simpler atomic bomb was a much higher priority. In 1950, after the Soviet Union had exploded its own atomic bomb the previous year, President Harry S. Truman directed the AEC to resume hydrogen-bomb development. Unfortunately, calculations suggested that there was no way of making it work. In addition, a committee of scientists strongly discouraged any attempt to build a hydrogen bomb, calling it “a danger to humanity” and “an evil thing.”

In 1951, however, the physicist Edward Teller and the mathematician Stanislaw Ulam came up with a brilliant new idea: Use an atom-bomb explosion to compress a cylinder of deuterium (a rare form of hydrogen) around a core of radioactive plutonium. The double whammy from implosion and radiation would fuse the deuterium atoms together into helium, releasing large amounts of energy in the process. Teller gained support for his clever scheme from hawkish politicians and wavering scientists, including J. Robert Oppenheimer, leader of the wartime Manhattan Project, who said that “when you see something that is technically sweet, you go ahead and do it.”

When the results of the test were announced, on November 16, the world’s nuclear tensions redoubled, as did America’s domestic obsession with atomic spies. Oppenheimer himself was barred from top-secret work in 1954 as a result of his 1930s Communist connections. The Soviet Union exploded its own hydrogen bomb in August 1953, and from then on things only got worse until the Nuclear Test Ban Treaty of 1963 began the long, slow process of withdrawal from the nuclear precipice.