Seventy years ago, at Operation Crossroads, nuclear weapons briefly became a form of consumer entertainment. Photograph Courtesy Library of Congress

On July 25, 1946, the United States Navy carried out the fifth detonation of an atomic bomb in history, in a lagoon at Bikini Atoll, in the South Pacific. The device was anchored about ninety feet beneath a barge, and when it exploded it sent up an immense column of radioactive seawater, topped by a flattened white mushroom cloud. The column rose some six thousand feet, then collapsed back into the lagoon, generating a wave that was nearly the height of the Chrysler Building. From the air, the explosion’s shock front could be seen racing across the lagoon toward an armada of ninety mothballed warships—American, German, and Japanese—which were moored nearby. By the time the chaos subsided, eight had sunk and many more had been damaged.

The very first nuclear test, a year earlier, was called Trinity, a name that evoked the intellectual mysticism of its chief scientific architect, J. Robert Oppenheimer. The test series at Bikini was given a less esoteric but perhaps more fitting moniker: Operation Crossroads. That was what 1946 was—a crossroads, a year of choices about the character of the postwar, newly nuclear world. Domestically, Congress was finalizing legislation that would transfer control of the nuclear arsenal from the U.S. military to the civilian Atomic Energy Commission. Meanwhile, at the United Nations, a committee was debating the possibility of placing atomic weapons under “international control” and creating a monitoring system that would prevent member countries from developing their own. It was a bold idea, championed by Oppenheimer, and would perhaps have wrought a very different future. In 1946, it looked like the bomb might just as easily lead to an era of international coöperation as one of arms races.

Crossroads was to consist of three test shots—Able, Baker, and Charlie—all aimed at the target fleet. Able would be dropped from a B-29 bomber, Baker set off on or under a barge, and Charlie detonated much deeper underwater against a group of salvaged submarines. Remarkably, the operation was not kept secret. More than a hundred and fifty ships were required to quarter the forty-two thousand people who witnessed it. Reporters, members of Congress, and representatives of the United Nations were invited to come and observe the tests. Even the Soviet Union was encouraged to send a delegation. Three Russians ended up attending, including Mikhail G. Meshcheryakov, an experimental physicist who would later become an adviser to the U.N.’s atomic-energy commission. The American military, of course, was keen to make sure that the Soviets and other foreigners were kept far from the bombs themselves, and indeed they were completely isolated, stuck on a ship for weeks and denied even press releases. A French representative later said that it was “the only exotic cruise on which I was bored.”

The official purpose of the operation, in principle, was to assess the vulnerability of naval formations to atomic attacks, which was a worthy goal from the Navy’s point of view. But with the United States as the world’s sole nuclear power, and the weapons in its stockpile numbering fewer than ten, Crossroads also came to be criticized as wasteful and frivolous. It was thought that it might furnish the military with some new data, but at the cost of a significant fraction of the arsenal. And because getting accurate data required absolute certainty about the explosive power of the bomb, the scientists at Los Alamos laboratory would not be able to test any new designs. They would be using carbon copies of the weapon that was dropped over Nagasaki.

The most urgent objections, though, centered on Baker and Charlie. There was considerable concern that detonating a bomb underwater could have unexpected, perhaps disastrous consequences. Percy Bridgman, a professor at Harvard University and the recipient of that year’s Nobel Prize in Physics, speculated in a letter to a colleague that “if the bomb is exploded in the ocean the hydrogen may be converted to helium with an astronomical release in energy.” This was an updated variation on the fear, first voiced before Trinity, that an atomic blast might set the atmosphere on fire. Bridgman didn’t think that the odds of such an accident were very high, but he anticipated a political backlash nonetheless. “Suppose the bomb is dropped as at present is planned, the ocean does not explode, and that later it should become known to the general public . . . that the scientists had permitted the taking of a stupendous chance without doing everything in their power to safeguard all possibilities?” The results, he continued, could be catastrophic. “There might well be a reaction against science . . . which would result in the suppression of all scientific freedom and the destruction of science itself.” This was worse, in Bridgman’s mind, than vaporizing the planet’s oceans, “which after all would not very much affect a world of dead men.”

Bridgman’s was a private worry, but there were more public outcries. Eventually, the panic over Crossroads prompted William Blandy, the vice-admiral in charge of orchestrating the tests, to release one of the more memorable official denials in modern history:

The bomb will not start a chain reaction in the water, converting it all to gas, and letting the ships on all the oceans drop down to the bottom. It will not blow out the bottom of the sea and let all the water run down the hole. It will not destroy gravity. I am not an atomic playboy, as one of my critics labeled me, exploding these bombs to satisfy my personal whim.

Even as the press fretted about the danger of Crossroads, it also cemented a new feature of the atomic age: nuclear kitsch. Shortly after the Able test, the Parisian fashion designer Louis Réard débuted a skimpy swimsuit, which he named after the atoll: the bikini. Blandy’s wife, in a much-reproduced photograph, was shown cutting a mushroom-cloud cake, with a hat that bore a noticeable, though apparently accidental, resemblance to the top of the cloud itself. Even the bomb crews got swept up in the furor, dubbing the Able weapon Gilda, after Rita Hayworth’s character in the film of the same name. The crew not only stencilled the name onto the bomb casing but also attached an image of the actress. (When word got back to Hayworth, according to Orson Welles, her husband at the time, she “almost went insane, she was so angry.”) The sombre ruminations prompted by Trinity, Hiroshima, and Nagasaki—What did it mean to possess the almost divine power to split the atom?—had been transmuted into gaudy sex symbols. The hand-wringing that would accompany the publication of John Hersey’s “Hiroshima,” later that summer, had yet to begin. Crossroads marked a moment of giddy abandon, when weapons of mass destruction became a form of consumer entertainment.

Rita Hayworth’s image affixed to the side of the bomb used in the Able test. Photograph Courtesy Los Alamos National Laboratory / Peter Kuran, VCE Films Photograph Courtesy Los Alamos National Laboratory / Peter Kuran, VCE Films

Perhaps not surprisingly, given the hype, Able proved a disappointment. The reporters were stationed more than twice the distance from ground zero as the scientists had been at Trinity; no one was knocked off his feet. Able also missed its target by half a mile, dramatically diminishing the damage it did to the ghost armada. The weapon exploded almost directly above the Navy’s data-gathering equipment, sinking one of its instrument ships, and a signal that was meant to trigger dozens of cameras was sent ten seconds too late. The newspapers lampooned the test. “The A-bomb is a distinctly overrated weapon,” one reporter wrote.

After the disappointment of Able, the stakes for the next shot were high. Fortunately, Baker could not miss, since the Navy had decided to anchor it in place. The technicians dubbed this weapon Helen of Bikini, and one of the congressmen in attendance was allowed to chalk “Made in New Mexico” on its caisson. Although the theoretical consequences of an underwater detonation had been studied by the members of the Manhattan Project, who built the Trinity device, this would be the first practical test. When an atomic bomb goes off, the resulting mushroom cloud contains a mix of highly radioactive bomb debris, unreacted bomb fuel, and anything unfortunate enough to get sucked into the fireball. For a surface shot, like Trinity, this meant dirt and desert sand; the cloud would drift for hours, dropping radioactive by-products as fallout. The question now was how the Baker explosion would differ. Would the weapon generate a tsunami? Would it be as powerful as a bomb detonated on land? Would it produce more radioactivity or less?