Joseph John Rochefort, the man whose decoding of the Japanese codebook led to the American victory at the Battle of Midway, had enemies other than the Empire of Japan. His feats at cryptanalysis were phenomenal, but not universally appreciated, particularly by the codebreakers in Washington, D.C. Naval jealousy and internal machinations would rob Joseph Rochefort of the honor that was due to him for his brilliant work in predicting where the Japanese fleet would strike after Pearl Harbor.

Rochefort, who had not gone to the Naval Academy, was an outsider from the beginning of his naval career. He was still in high school when he enlisted in the Navy in 1918 with the goal of being a naval aviator. He claimed to have been born in 1898 so that he would seem old enough for a military career, and didn't even have a high school diploma when he was commissioned as an ensign after graduating from the Navy's Steam Engineering School at Stevens Institute of Technology.

He wasn't looking for a career in codebreaking. He served as a staff officer for senior admirals and and enjoyed doing crossword puzzles. Years later, when Commander Chester C. Jersey was posted to Navy Headquarters in Washington, D.C., he remembered Rochefort's affinity for crossword puzzles. It was 1925 and the Navy was looking for people who could work with codes. The newly created codebreaking outfit of the Navy, OP-20-G, at that time consisted of one man, Lieutenant Laurance F. Stafford, today credited as the father of U.S. Navy cryptology, who had been assigned to develop new codes for the Navy. Rochefort showed up and Safford conducted a six-month cryptanalyis course: Safford provided him with cryptograms to solve and Rochefort solved them. But when Stafford was assigned to sea duty the following year, Rochefort, just twenty-five years old, was the officer in charge of a staff of two. By June 1941, Rochefort was at Pearl Harbor. By this time, the codebreaking unit had more people and, more relevance. The Japanese didn't know that their code had been broken years before when a previous American Director of Naval Intelligence used a secret naval intelligence slush fund to finance break-ins during the early 1920s at the Japanese consulate in New York City. The Japanese Navy's code book was furtively photographed and, over the years, translated. By the time he was sent to Station HYPO at Pearl Harbor, Rochefort had the codebook. But he didn't have the additive tables, which the Japanese frequently changed. Rochefort's assignment was to create an accurate additive table using the raw messages that went out over the airwaves by the Japanese Navy.

Joseph John Rochefort.

The Japanese attack on Pearl Harbor on December 7, 1941, was a devastating blow to the Navy, but it also galvanized the nation and its military forces into the war effort. Restoration began immediately on the naval fleet. But in order to defeat the Japanese and their intention of becoming the dominant naval power in the Pacific, the Navy knew that codebreaking was a crucial priority. Fortunately, in Joseph Rochefort, they had a codebreaker who worked tirelessly to decipher the messages of the Japanese. Joseph Rochefort and his crew had been given the order to begin the decryption of JN-25, the central Japanese communications system. As it turned out, breaking the Japanese code would prove easier than addressing the friction between Station HYPO at Pearl Harbor and OP-20-G in Washington, D.C. Captain Edwin Layton was the Pacific Fleet's intelligence officer. But, because OP-20-G had given Rochefort the assignment and was more or less overseeing the network of the intercept stations, there was a turf war between Rochefort and Washington, D.C. The D.C. office wanted central control over all of the radio intelligence units. Rochefort, who was not always as tactful as might have been politic, believed that he answered solely to Admiral Nimitz, who had been named commander of the Pacific Fleet. Layton had a great deal of respect for Rochefort's factual reports and hard work; he, like Rochefort, was fluent in Japanese and Layton knew how much work was going into the messages that were being translated. In fact, of the five hundred to one thousand messages per day that were being deciphered, Rochefort was personally translating more than one hundred of them. Layton trusted Rochefort's translation and his assessment, so when Rochefort called Layton on May 14, 1942, to say that he had translated part of a message which included the words "invasion force", Layton knew it was legitimate. But the message also include an unknown reference, AF, indicating a location. But where was AF? Rochefort was convinced that the location was Midway.

Nimitz agreed with Rochefort's analysis and ordered three aircraft carriers to return from the South Pacific. Midway was covertly warned of the threat. The Seventh Air Force at Hawaii was placed on alert, its B-17 bombers loaded with bombs ready to strike enemy ships.

Commander John Redman, who commanded OP-20-G, refused to believe that Midway was the next Japanese target, disputing Rochefort's assertion that AF was Midway. OP-20-G said the target was more likely to be the Hawaiian Islands but thought that the real target was the American West Coast and everything else was merely a decoy.

Captain Edwin Layton.

But Nimitz had complete confidence in Rochefort's analysis. If Rochefort was wrong, Nimitz's career would be imperiled. Rochefort devised a plan that would confirm that Midway was the target. The radio operators at Midway were instructed, via undersea cable, to send an uncoded message that the island's distillation plant, which was responsible for the desalination of the island's water supply, had broken down. Two days after the message was sent, the Japanese reported that the AF Air Unit needed to be resupplied with fresh water. The Navy intercept unit in Australia informed Washington that AF was now confirmed to be Midway. Rochefort spent the night before Nimitz's May 27, 1942 staff meeting reviewing all the messages. He showed up at the meeting to let them know that HYPO had broken the final piece of the JN-25 puzzle; he had a message dated for May 26 ordering the destroyer escorts for the Japanese troopships to arrive at Midway on June 6. Another decoded message said that the air attacks would begin northwest of the island several days before.

Rochefort's reports came in the nick of time. On May 27, both the code books and the additive tables were changed and radio silence was imposed by the Japanese, denying American codebreakers access. Fortunately, Nimitz had his cues, knowing where and when the Japanese would strike. Nimitz was not a codebreaker, but he had an instinct for the future of naval warfare and he held the radical view that carriers, and not battleships, would lead to victory. Instead of relying on the few battleships that had survived the attack on Pearl Harbor, he focused on the ability of the carriers to deliver hit-and-run attacks against the enemy. Japanese Admiral Isoroku Yamamoto, the mastermind of the December 7 ambush, had an elaborate plan for the Midway attack. Nimitz had a simpler approach: get there first and surprise the Japanese. The tactics worked. As British Prime Minister Winston Churchill, formerly First Lord of the Admiralty, put it, "The annals of war at sea present no more intense, heart-shaking shock…the qualities of the United States Navy and Air Force and the American race shone forth in splendour". After the victory, Station HYPO celebrated for what Rochefort described as a "drunken brawl" for three days. The codebreakers then returned to work to decode JN-25's new codebook and additives. They had done splendid work that had resulted in a gamechanging victory at sea. But Washington was not so charitable in its response. Rochefort was resisting Redman's crusade to place all the radio intelligence under the control of OP-20-G in Washington, D.C. Although both HYPO and OP-20-G had been vigorously involved in the codebreaking, it was HYPO which had performed the analysis that had led to victory. As author Stephen Budiansky points out in his book Battle Of Wits: The Complete Story Of Codebreaking In World War II, if Nimitz had followed Washington's direction, the Japanese would have had a much greater chance of winning at Midway.

Admiral Isoroku Yamamoto.