On the morning of July 25, 1946, a bomb hung on a cable beneath a small landing ship in the middle of Bikini Lagoon, about 90 feet below the surface. Around it, anchored in deliberately tight rows, sat a fleet of more than 90 warships with no crews aboard: old American battleships, two aircraft carriers, submarines, transports, and three surrendered enemy vessels, including the Japanese battleship that had served as the flagship for the Pearl Harbor attack. At 8:35 a.m. the bomb went off. The landing ship it hung from was never found again.
The test was called Baker, and it was the second half of Operation Crossroads, the first nuclear explosions since Nagasaki. The Navy wanted to know whether a fleet could survive an atomic bomb. The answer it got was stranger and more troubling than “yes” or “no.” Most ships stayed afloat. Almost none of them could be made safe again. The chemist Glenn Seaborg, who later chaired the Atomic Energy Commission, called Baker “the world’s first nuclear disaster.”
A test built around an argument
Crossroads began as a fight over budgets as much as physics. In August 1945, days after the war ended, the future Atomic Energy Commission chairman Lewis Strauss warned the Navy secretary that without a test there would be “loose talk to the effect that the fleet is obsolete in the face of this new weapon.” Army Air Forces officers suspected the opposite and wanted a demonstration that bombers had made battleships pointless. President Truman eventually set up a civilian review panel so the public would believe the results were “on the level.”
The Navy picked Bikini, a coral atoll in the Marshall Islands, because it was remote, had a lagoon big enough to hold a fleet, and had a small population that was easy to move. The 167 people who lived there were told in February 1946 by a Navy commodore who compared them to the children of Israel being led to the Promised Land. In March they were shipped 128 miles east to Rongerik Atoll, which could not feed them. Within a year visitors were reporting malnutrition. Their descendants still have not been able to go home for good.
The operation itself was enormous: about 42,000 people and more than 150 support ships. Radio-controlled B-17 drones flew cameras and air samplers into clouds no crew could survive, and the task force shot about 50,000 photographs and 1.5 million feet of film.
The goats on the gun turrets
Scientists objected that the tests would measure what happened to steel while ignoring what happened to sailors. The task force commander, Vice Admiral William Blandy, answered by putting animals where the crews would have been. The support ship USS Burleson arrived with 200 pigs, 60 guinea pigs, 204 goats, 5,000 rats, 200 mice, and grain full of insects for genetics studies. For the first test, roughly 3,500 animals were placed at sailors’ stations on 22 target ships, some tethered on open decks and some deep inside armored turrets.
The first shot, Able, came on July 1. A B-29 named Dave’s Dream dropped a Fat Man-type bomb nicknamed Gilda, stenciled with a picture of Rita Hayworth. It burst 520 feet over the lagoon with a yield of 23 kilotons — and missed its aim point, the orange-painted battleship USS Nevada, by about 710 yards. Nobody ever settled why. Five ships sank. Many of the 114 reporters watching from 10 nautical miles away were underwhelmed; sailors described a small, distant “poom.” The New York Times said only two ships had gone down.
The animals told a darker story. About a third of the Able animals died in the following months, killed by blast, by radiation, or by researchers studying them. Goat 119, tied inside one of Nevada’s armored gun turrets, survived the blast and died of radiation sickness four days later. The Bulletin of the Atomic Scientists summed up the lesson: a big ship a mile from the explosion might stay afloat, but its crew would be dead, leaving “only a ghost ship” drifting on the ocean.
The most famous survivor was Pig 311. According to the legend, repeated by TIME in 1949, she had been locked in an officers’ washroom on the Japanese cruiser Sakawa, which burned and sank, and was later found swimming in the lagoon. She grew to about 600 pounds and retired to the National Zoo in Washington. Later digging suggests she may simply have gone missing from her post before the test and turned up when the other pigs were rounded up.
Baker: a geyser a mile high
Baker produced so many new effects that the task force held a conference afterward just to name them. The fireball formed underwater as a giant bubble of hot gas. Its shock wave raced through the water at about a mile per second, crushing nearby hulls, and showed on the surface as an expanding dark ring called the “slick.”
Four milliseconds after detonation, the bubble touched the lagoon floor and the surface at the same time. It dug a crater about 2,000 feet across and threw up a “spray dome.” Within a second it had cleared a 500-foot radius of water and hurled about two million tons of seawater and seabed sand into the sky. That mass rose into a hollow column about 6,000 feet tall and 2,000 feet wide, with walls 300 feet thick. For two seconds a “Wilson cloud” — instant fog formed behind the shock wave — hid it from view.
Then it all came down. The battleship USS Arkansas, closest to the bomb, had her starboard hull crushed and rolled over onto the bottom. A wave 94 feet high spread out from the center; by the time it reached Bikini Island’s beach three and a half miles away, it was still throwing landing craft onto the sand. The carrier USS Saratoga, which had survived a fire after Able, had her stern lifted 43 feet, lost every plane on her deck, and slowly flooded. She sank seven and a half hours later.
But the most important effect was the one that looked least violent. About 12 seconds after detonation, water falling from the column formed a ring of mist around its base, like the spray at the bottom of a giant waterfall. This “base surge” was about 900 feet tall. According to the task force’s technical report, it swept outward at roughly 45 miles per hour and reached nearly 8,000 feet from the center, rolling across most of the fleet. It carried the bomb’s fission products with it. All but nine of the target ships ended up heavily contaminated.
Scrubbing a fleet with soap and lye
An air burst like Able, or the bombs over Hiroshima and Nagasaki, carries most of its radioactive debris up into the stratosphere. Officials at the time called this “self-cleansing.” Baker was not. It mixed about three pounds of fission products and more than ten pounds of plutonium that never split into the lagoon, then sprayed the result over the fleet. Seawater added its own hazard: neutrons turned ordinary sodium into sodium-24, which is intensely radioactive for days and contaminated the pipes and hulls of support ships that entered the lagoon.
Nobody had tested a cleanup method, so the Navy used the one it knew. In the first six days, about 4,900 sailors boarded target ships with hoses, mops, brushes, soap, and lye. The first hosing cut radiation roughly in half; after that, almost nothing changed. Only sandblasting down to bare metal really worked. The sailors had no protective clothing, and they tracked contamination back to the showers, laundries, and bunks of the support ships.
The danger the Geiger counters couldn’t see
The man responsible for radiation safety was Colonel Stafford Warren, the Manhattan Project’s chief medical officer, who had also overseen safety at Trinity and the ground surveys at Hiroshima and Nagasaki. By early August he was convinced that the cleanup was pointless and dangerous. His team had issued 18,875 film badges and was pulling anyone with more than 0.1 roentgen a day off the ships. Badges recorded 67 overexposures in four days. More than half of the 320 Geiger counters on hand had shorted out in the salt and humidity.
Warren’s real worry was something none of those instruments could detect. Plutonium gives off alpha particles, which are stopped by paper, skin, or the glass wall of a Geiger tube. Outside the body that makes it fairly harmless; breathed in or swallowed, it lodges in bone and stays. The Navy’s plan assumed that if sailors scrubbed off the gamma-emitting fission products they could measure, the plutonium would wash away too. Lab tests aboard the hospital ship USS Haven showed it did not.
Ship captains pushed back; one accused Warren’s monitors of holding their counters too close to the deck. What finally changed Blandy’s mind, on August 10, was a picture. Warren had laid a surgeonfish from the lagoon on a sheet of photographic film overnight. The fish had taken its own X-ray: alpha radiation from plutonium spread through its body, all the way to the scales, had exposed the film in the shape of the fish. Blandy looked at it and said, “Then we call it all to a halt.” Warren wrote home that “a self x-ray of a fish … did the trick.” One of his monitors later called him “the only Army colonel who ever sank a Navy flotilla.”
A fleet that couldn’t come home
The cleanup stopped 16 days after Baker. A third test, Charlie — a deep underwater shot planned for 1947 — was canceled, officially because it wasn’t needed, in practice because there were no clean ships left and the crews were tied up. The Navy towed the surviving targets to Kwajalein to unload fuel and ammunition, and quietly decided that any ship sunk more than 30 days after Baker “will not be considered as sunk by the bomb.”
In the end, only nine target ships were clean enough to be scrapped. The rest were scuttled off Bikini, Kwajalein, Hawaii, or California between 1946 and 1948. The German cruiser Prinz Eugen, too radioactive for her leaks to be repaired, capsized in Kwajalein lagoon that December; her propellers still stick up out of the water. New Navy ships were later built with “washdown” sprinklers to coat their decks with flowing seawater before fallout arrived.
The public mostly missed the story. The reporters had gone home before the cleanup failed, and the official reports came out a year later. Many people only learned about it in 1948, from No Place to Hide, a bestselling account by David Bradley, a doctor who had worked as one of the “Geiger men” at Bikini. His description of radioactive ships that could not be scrubbed clean brought fallout into everyday conversation.
What it did to the people involved
The health toll on the roughly 40,000 Navy participants has been hard to pin down. A 1996 Institute of Medicine study comparing them with similar sailors who weren’t at Bikini found about 4.6 percent higher overall mortality over the following decades. Oddly, deaths from cancer and leukemia were not significantly higher, and the researchers could not explain the gap. A 1988 law stopped requiring atomic veterans to prove that certain cancers came from the tests.
For the people of Bikini, there was no ambiguity. The United States returned to the atoll in the 1950s and set off 21 more nuclear tests there, including the 15-megaton Castle Bravo shot of 1954, the largest American test ever, whose fallout injured islanders on nearby Rongelap. A resettlement attempt in the 1970s ended when people who had moved back were found to be absorbing radioactivity from local food.
The ghost fleet today
Bikini Lagoon now holds one of the strangest wreck sites in the world. Saratoga sits upright on the bottom, the top of her mast about 40 feet below the surface. Arkansas lies upside down on the rim of the Baker crater. When the first Navy diver reached her in 1946, he sank up to his armpits in radioactive mud; when National Park Service archaeologists returned in 1989 and 1990, the mud was gone and the bottom was firm sand again. Divers who visit still have to eat food brought in from elsewhere.
Crossroads also left a word behind. That July, the Paris designer Louis Réard named his tiny new two-piece swimsuit after the atoll because, like the bomb, it was “small and devastating.” The Baker footage stuck around too, turning up in Dr. Strangelove and Godzilla.
What makes Crossroads worth remembering isn’t the size of the explosions. By later standards 23 kilotons is small; the hydrogen bombs that followed were hundreds of times larger, and one was even set off in space in Starfish Prime. It’s what the test revealed about contamination: you can’t hose it off, the most dangerous part may be invisible to your instruments, and a ship can look intact while being impossible to use. When Blandy finally grasped the plutonium problem, the precedent he had in mind was the Radium Girls, the dial painters poisoned by tiny amounts of swallowed radium.
Related reading on aglena: the Halifax Explosion, the largest man-made blast before the atomic age; Oklo, the natural nuclear reactor that ran for hundreds of thousands of years without anyone to clean up after it; and Project Azorian, another Cold War story about what lies on the floor of the Pacific.
Further reading
Radiacode-102 Smart Radiation Detector and Gamma Spectrometer
A pocket scintillation detector that pairs with a phone app to map gamma readings and show the energy spectrum, so you can tell cesium from radium — the kind of instant answer the Geiger men at Bikini never had. Like their counters, it can’t see alpha emitters such as plutonium.
Operation Crossroads: The Atomic Tests at Bikini Atoll by Jonathan M. Weisgall
The standard history of the 1946 tests, from the Navy-versus-Air-Forces politics and the Bikini islanders’ exile to the failed cleanup of the target fleet.