May 1942. The fake water shortage that sank four Japanese carriers. By mid-May 1942, the US Navy had a problem. They had broken into the Japanese fleet operational code, JN-25, well enough to read fragments of it. They could see Admiral Yamamoto assembling something enormous. Four fleet carriers. A diversionary attack against the Aleutians. A landing force. The target was identified in every transmission by a single two-letter codeword: AF. Joseph Rochefort, the eccentric cryptanalyst who ran Station HYPO out of a windowless basement in Pearl Harbor known as "the Dungeon," was certain AF was Midway. He worked 20-hour shifts in a red smoking jacket and bedroom slippers because the basement was freezing. He survived on coffee and sandwiches passed in through the door. Washington disagreed. The Navy's main code-breaking section, OP-20-G, thought AF was probably the US west coast, possibly Hawaii itself, possibly even the Panama Canal. Admiral King in Washington trusted his own people. Admiral Nimitz at Pearl Harbor trusted Rochefort. One of them had to be wrong. Rochefort's deputy, Jasper Holmes, came up with the trick. Midway was instructed to broadcast a radio message in plain, uncoded English. The garrison's freshwater distillation plant, the message said, had broken down. They were running short of water and requested an emergency tanker. The message was fiction. The plant was fine. Two days later, American listening stations intercepted a Japanese intelligence transmission, encrypted in JN-25, reporting back to fleet headquarters that "AF is short of fresh water." AF was Midway. Confirmed. Nimitz now knew where, when, and with what. He positioned his three available carriers, Enterprise, Hornet, and the half-wrecked Yorktown, in ambush 325 miles northeast of the island. Yorktown had been hit at the Battle of the Coral Sea two weeks earlier and was supposed to need 90 days in dry dock. Pearl Harbor's shipyard repaired her in 72 hours. On June 4, 1942, in roughly six minutes between 10:22 and 10:28 AM, American dive bombers caught three Japanese carriers, Akagi, Kaga, and Soryu, with their decks loaded with fuel and ordnance for a strike they were about to launch. All three were burning hulks by lunchtime. Hiryu was sunk that evening. Japan lost four fleet carriers, a heavy cruiser, 248 aircraft, and over 3,000 men, including most of the irreplaceable veteran naval aviators who had attacked Pearl Harbor six months earlier. Joseph Rochefort was rewarded with reassignment. His rivals in Washington saw to it that he was pushed out of cryptanalysis entirely and given command of a floating dry dock in San Francisco. He spent the rest of the war repairing ships. He received the Distinguished Service Medal for Midway in 1986, ten years after he died.