Japanese heavy cruiser Mikuma burning at Midway
National Archives and Records Administration
THE COMMANDER IN CHIEF OF THE US PACIFIC FLEET, NAVY ADMIRAL Chester W. Nimitz, did in fact know plenty about Admiral Yamamoto’s intended May 1942 move on Port Moresby, thanks to intelligence provided largely by US code breakers stationed in Hawaii. For weeks and with increasing specificity, the team had decrypted Japanese naval transmissions indicating that warships and transport ships filled with troops were assembling at the Imperial Navy’s main base at Truk Lagoon in the central Pacific and that the force was preparing to head south to the Coral Sea. Many of the initial messages contained the sign “RZP,” which code breakers had previously established was a geographical designation for Port Moresby. But cryptanalysis is never a straight line. On April 24, a new term appeared in the Japanese transmissions: “MO.” The term was used in several contexts, as in “MO fleet,” or “MO occupation force.” The code breakers were stymied, uncertain if the term was connected to Port Moresby or referred to another operation altogether.
The unit’s chief, Commander Joe Rochefort, put the mystery term into the hands of a pair of star linguist-cryptographers—Major Alva “Red” Lasswell and Lieutenant Commander Joseph Finnegan. Finnegan insisted that “MO” meant Port Moresby, not to be confused with its geographical code name (which was RZP) but as an operational code name for the Port Moresby invasion. When Lasswell separately reached the same conclusion, Rochefort felt they had unraveled Admiral Yamamoto’s next move. Further confirmation came five days later, on April 29, when Yamamoto’s Operation Order No. 1, transmitted to Vice Admiral Shigeyoshi Inoue, was intercepted. Rochefort’s men decrypted the order, which read as a pep talk from Yamamoto to the vice admiral charged with leading the Fourth Fleet’s imminent conquest of Port Moresby. “The Imperial Navy will operate to its utmost until this is accomplished,” Yamamoto wrote. The message left no doubt about the decryption of “MO” as the code name for the invasion of “RZP.” The code breakers rushed their intelligence about Port Moresby to Nimitz, who was able to plan accordingly. Yamamoto’s Imperial Navy was anticipating a surprise attack in early May 1942—and yet another Pacific triumph—but was instead the one surprised. Nimitz’s forces fought Yamamoto’s to a standstill on May 7 and May 8 in the Battle of the Coral Sea.
SINCE THE PEARL HARBOR ATTACK THE PREVIOUS DECEMBER, RED Lasswell had emerged as one of the most valuable and productive talents in the decrypt unit known as Station Hypo. For all of his linguistic skill and affinity for numbers, the lanky, sandy-haired Lasswell, who had grown up in rural Piggott, Arkansas, had never earned so much as a high school diploma. The lone marine in a code-breaking unit largely made up of naval officers, he’d had to take a correspondence course in 1925 to gain acceptance into the Marine Corps’s Officer Candidate School. Now, at Station Hypo, he had established himself as a measured and precise analyst, a workaholic among workaholics who always wore a green eyeshade to block the glare of fluorescent lighting and smoked either Cuban cigars or a pipe as he huddled over his work at a tidy gray metal desk. Unit commander Joe Rochefort liked pairing Lasswell with fellow Hypo linguist Joe Finnegan, an intense chain smoker from Boston whose desk was usually piled high with intelligence notes, a mess only he could fathom. Finnegan was more freewheeling in his approach to cracking a Japanese message, relying on intuition and an infallible memory for retrieving data from prior transmissions. Rochefort saw Finnegan as complementary to Lasswell, the yin to his yang.
They worked in a windowless room in the basement of a nondescript navy administration building at Pearl Harbor nicknamed “The Dungeon.” Rochefort’s desk was at one end, the way a teacher’s desk is positioned in front of a classroom. To his right were the traffic analysts, whose job it was to study the “externals” of radio transmissions—the volume, location, and senders—and based on those determine the Japanese fleet’s whereabouts. To Rochefort’s left sat the language officers Lasswell and Finnegan, while directly in front were desks for the information specialists with tables of maps, files, and books. Seated at the other end were the cryptanalysts, whose uncanny mathematical skills were key to deciphering coded groups of numbers into text that Lasswell, Finnegan, and their staff then translated into English. Though the cryptanalysts and translators worked hand in hand, Rochefort considered the latter to have the most essential function. “You can assign values and all that sort of thing,” he said later about the important first step performed by cryptanalysts, “but unless you do a good job of translating the whole [effort] is lost.”
Station Hypo was one branch in the navy’s cryptologic program, the largest signals intelligence program of any of the US military services. Observing at a distance Japan’s rapid naval expansion during the 1930s, prescient US naval leaders had seen a corresponding need to expand their service’s intelligence-gathering capability and to exploit the advantage US code breakers had from years of deciphering various codes used by the Imperial Japanese Navy. Radio intercept stations were set up on tiny islands throughout the Pacific, including Hawaii, that, like a net, captured Japanese radio transmissions. Three code-breaking outposts, up and running by decade’s end, then worked on deciphering the messages. The unit in Washington, DC, known as OP-20-G, served as headquarters. A second outpost, known as CAST, was in Cavite on the island of Luzon in the Philippines; it would have to relocate to Melbourne, Australia, when the Philippines fell to the Japanese. Station Hypo at Pearl Harbor was the third location. Over time, and especially after the Pearl Harbor attack, intense rivalry flared as the units competed to be the first to decipher messages quickly—and accurately. In addition, throughout the 1930s, the navy sent prospective code breakers to Japan for three-year tours to gain fluency in the language, mingle with Japanese naval officers socially, and develop a sense of the local customs and culture of a possible future enemy. Joe Rochefort, Station Hypo’s eventual commander, had participated in the program, as had Joe Finnegan. In the shadow war for intelligence, the navy program would prove itself far superior to its Japanese counterpart.
Red Lasswell had also participated in the navy’s language immersion course. His colonel, noting that the program was seeking a marine in the mix, had pushed him to volunteer despite his lack of education credentials. Lasswell had spent 1936 to 1938 in Tokyo, fast becoming an expert in the language and forging a bond with Finnegan during the two years they overlapped. Finnegan, he later said, “was my good right arm during World War II.” In the late 1930s, Lasswell followed Finnegan to the outpost in Cavite, and it was there he was “first indoctrinated into the work that later occupied me during the war.” By that Lasswell meant he began work in earnest as a code breaker—not just translating but also developing the ability as a cryptanalyst to break coded number groups into words. That was why he and Finnegan became so valued; they were hybrids, both linguists and analysts. In the spring of 1941, Lasswell was transferred to Pearl Harbor to work for Rochefort at Station Hypo, officially known as Fleet Radio Unit Pacific Fleet (FRUPAC).
That fall, US code breakers at Hypo and elsewhere had had a sense that war with Japan was imminent, but no one had detected the coming of Yamamoto’s surprise attack on Pearl Harbor on December 7. Rochefort later unblinkingly bemoaned the collective failure, saying “an intelligence officer has one task, one job, one mission. That is to tell his commander, his superior, today, what the Japanese are going to do tomorrow.” Lasswell was on overnight duty the morning of the attack. “I was at the office and watched the bombers come in,” he said. “I was just as surprised at the moment in which it started as anybody else there.”
DURING THE WINTER AND SPRING OF 1942, IT WAS AS IF THE CODE breakers at Station Hypo were determined to make up for Pearl Harbor. Japan’s navy was old school in the sense that it favored codebooks over emerging machine technologies. The words and information contained in the books were converted to number groups—each of five digits, of which there were some 50,000 in total—that communication specialists strung together to create a coded message. The coded number groups were then embedded in other groups of numbers, a process called superencipherment, to make it more difficult for Allied code breakers to determine which of the number groups made up the actual message. But during that period, code breakers had penetrated the Imperial Navy’s main code, which was called JN-25, short for “25th Japanese naval code.” The code-breaking challenge was adjusting to changes the Japanese introduced periodically for security reasons, when they altered the numerical equivalents of words. The change to the latest edition, known as JN-25(b), had not thrown off the Allied code breakers, however. That winter, Rochefort’s men at Station Hypo and code breakers at the other Allied outposts had been all over JN-25(b). It was the successful deciphering of JN-25(b) messages that had given them a heads-up in early spring about Yamamoto’s bid to attack Port Moresby. And if Yamamoto was surprised by the outcome of the Coral Sea battle, he was in for an even bigger surprise regarding the critical naval operation he was developing and personally planning to direct: invading Midway.
By early May 1942, Japanese naval radio traffic was off the charts, an explosion that practically overwhelmed the US Navy’s radio intercept nets throughout the Pacific. The radiomen at the Wahiawa station in central Hawaii, for example, found themselves delivering huge bundles of raw intercepts by courier to Station Hypo at Pearl Harbor, and the arrival of five hundred to a thousand intercepts a day radically altered life in the Dungeon. “From a monastery the place turned into a pressure cooker,” one historian noted. In a bid to cope with the surge, Lasswell and Finnegan set up a two-watch system in which one of them would work a twenty-four-hour shift overseeing the less experienced translators and the other would then take over for the next twenty-four hours. That way one of Hypo’s star linguist-cryptanalysts was always on duty. Even though they were working around the clock, they still didn’t have enough time to process everything coming over their desks. Lasswell set up a cot behind his table. “I would use it to doze until I felt refreshed enough to go back to work.” To maintain the brutal work pace, a number of the men began popping amphetamines.
One worrisome discovery was the Japanese navy’s plan to implement a new version of its main code, replacing JN-25(b) with JN-25(c), effective May 1, 1942. For the code breakers, the intelligence amounted to good news, bad news. On the one hand, the tightening of communications security suggested that the Imperial Navy was gearing up for something big. On the other hand, until the code breakers managed to crack the new edition of the code, they’d be at a loss to figure out Yamamoto’s plans. What Rochefort, Lasswell, Finnegan, and the others were not aware of, however, was the logistical hurdle the Japanese navy faced phasing in its new code—a consequence of its wildly successful expansion throughout the Pacific during the winter. With naval operators scattered all over the Pacific, the distribution of new codebooks was no easy task, so much so that May 1, 1942, came and went and the Japanese navy was still relying on JN-25(b)—and would continue to do so until the end of May, when the new version was finally activated.
Rochefort’s men hardly complained about Japan’s failure to switch to its new code come May 1; they and other Allied code breakers in Australia and Washington, DC, continued to pile up inside information on Yamamoto’s developing operational plans, practically looking “over Yamamoto’s shoulder as he moved his forces around the Pacific,” as Rochefort’s biographer later described the US advantage. In early May, the Hypo code breakers were picking up repeated references to an upcoming campaign. On May 5, they intercepted a message from Yamamoto’s fleet to Japan’s Navy Ministry to speed up delivery of fueling hoses, which told the Americans that Yamamoto’s attack fleet would be needing to refuel at sea. Then, on the afternoon of May 13, the decryption of a message from Yamamoto’s 4th Air Attack Squadron to the transport ship Goshu Maru provided a vital clue. The small ship, containing equipment to establish an air base and ground crews to service it, was ordered to Saipan, a Japanese stronghold. The ship was told it would join Japanese carriers and warships gathering at Saipan to sail toward “AF.”
The analysts recognized AF as a geographic symbol, the same way RZP stood for Port Moresby. They had previously deduced that AF was the designator of Midway Island but had not seen AF in the enemy’s radio traffic for at least two months. Other messages pouring in revealed that Yamamoto had assigned the same commander who had overseen the Pearl Harbor attack, Vice Admiral Chuichi Nagumo, to lead this strike force. (The code breakers never learned, however, that Yamamoto himself would be sailing behind Nagumo’s carrier fleet aboard his flagship, Yamato.) That Japanese ships were meeting at the central Pacific island of Saipan also fit as the most likely location from which to stage an attack on Midway Island. The Hypo cryptanalysts ranked decryptions from A to WAG. The highest, A, ranking meant that they were positive about their analysis—“As having been determined by more than one source and having turned up in radio traffic numerous times, removing any possibility of doubt.” The lowest, WAG, ranking stood for “wild assed guess.” Rochefort and his men put their assessment of AF at the highest ranking of reliability. They were certain that they’d figured out Yamamoto’s next target: Midway Island.
But their rivals at headquarters in Washington—at OP-20-G—didn’t buy it. No one at any of the code-breaking outposts disputed that Yamamoto was plotting a major operation, but the code breakers at OP-20-G did not accept that AF stood for Midway Island. The disagreement grew bitter. It wasn’t as if Washington could agree on an alternative. Some argued that Yamamoto’s target was Hawaii; others said San Francisco. Some floated the idea that even if AF did stand for Midway, it was part of a hoax Yamamoto had concocted to disguise his true intention: attacking Hawaii or the West Coast. Rochefort and his men, firm in their decryption, considered the opposition idiotic. Tension persisted at the highest levels, and for Admiral Nimitz the stakes on where to deploy his fleet were huge; a mistake could be catastrophic for the Pacific war. “Our fleet was then limping back from the battle of the Coral Sea,” Lasswell said, “and Admiral Nimitz had to make fast decisions about repairs to ships, refueling, re-ammunitioning, adding personnel.”
Lasswell started a shift on May 19 by going through a stack of raw intercepts freshly delivered to the Dungeon. He had flipped through fifty or so messages considered high priority when he detected what looked to be an important message. Two things jumped out at him. The first was that the message was from Yamamoto. The second was the list of people to whom the message had been sent: it was directed to just about every important Japanese naval command. Lasswell dug in. He worked all night to identify the unknown code groups and the next morning distributed a deciphered message that was nothing short of eye-popping: operational details of the Japanese navy’s attack on Midway, including the location of Nagumo’s carrier fleet northwest of the island. “I was able to give them the longitude and latitude from which these carriers were going to launch their planes.” But once again Washington did not buy Hypo’s conclusion that AF was Midway. Lasswell was furious. “I was sure of myself but others thought I was wrong.”
What to do? Others at Hypo began working feverishly to further backstop Lasswell’s decryption. Meanwhile, Rochefort, under mounting pressure from his superiors to put the controversy to rest, put into play a plan he and a small group at Hypo had devised the previous day. The idea had been Lieutenant Commander Wilfred J. “Jasper” Holmes’s. Holmes was an information officer who was an engineer by training. He had never been to Midway Island but knew that drinking water was a constant concern at the navy base there. He suggested that the Midway base transmit an urgent message reporting that the desalinization plant had broken down and a freshwater barge should be sent from Pearl Harbor immediately. It was the kind of intelligence that Japanese radio signal units would pass up the chain of command right away. Rochefort made the necessary arrangements, and the dispatch went out. To make it easy to read, the faux water shortage at Midway was reported in plain text, not coded.
Within hours, on the morning of May 20, Hypo’s Joe Finnegan was deciphering a message sent from the Japanese outpost on Wake Island to Tokyo, reporting a water emergency at a US Navy base in the Pacific. “The Japanese took the bait like hungry barracuda,” Holmes wrote later. Most important, the Japanese message used AF as the geographical designation to identify the island where the US base was located.
The ruse had worked. Beyond any doubt, the designator AF had been verified to mean Midway Island. Five days later, on May 25, the Japanese Imperial Navy finally altered its code to JN-25(c). “There was a big change,” Lasswell said, “so that we were back in the dark again.” But it was too late. The code breakers had gotten what they needed. With the treasure trove of intelligence, Admiral Nimitz began amassing a force of ships, the idea being to ambush the ambushers.
ON THE FIRST DAY OF JUNE, ISOROKU YAMAMOTO STOOD ON THE combat bridge of the 72,000-ton Yamato, the new flagship of the Combined Fleet and the most powerful battleship ever built by the Japanese. Sailing eastward toward Midway Island, Yamato was at the forefront of the Main Body, an armada under Yamamoto’s immediate command consisting of thirty-three other ships. Included were two more battleships, Nagato and Mutsu, a destroyer division, a cruiser division, and two light aircraft carriers. Yamamoto looked out over the open sea knowing that six hundred miles ahead of his armada was the attack force commanded by Vice Admiral Nagumo. Known as Kido Butai, meaning “Mobile Force,” Nagumo’s fleet included destroyers, battleships, and light cruisers that spread out in a circle surrounding its key assets: four of the Imperial Japanese Navy’s six large aircraft carriers. Elsewhere in the Pacific, transport ships carrying three thousand army soldiers and two battalions of the navy’s special land unit were on route to meet up with Kido Butai closer to the final destination. In all, Yamamoto and his staff had put together a force that was larger than the one used in the surprise Pearl Harbor attack six months earlier.
The Midway plan called for more than a hundred bombers from Nagumo’s carriers to pulverize the US base at Midway starting on June 4, crippling its defenses and grounding its planes ahead of an invasion by five thousand troops two days later. When the US Navy, alarmed at the prospect of losing Midway, dispatched aircraft carriers to resist the Japanese invasion, Yamamoto and his Main Body would ambush and obliterate the carriers. It was Yamamoto’s second chance to force an early peace in an unwanted war.
Coordinating the massive force had taken weeks. In early May, Japanese warships, including Yamato, had begun gathering in southern Hiroshima Bay. The deep waters of the bay’s Hashirajima anchorage were a favored staging area; in fact, Yamamoto had monitored the Pearl Harbor attack from Hashirajima. From the anchorage, ships requiring last-minute repairs and fueling sailed into the navy base at Kure, nineteen miles away. Yamamoto’s flagship did so on May 13, and the next six days in Kure were a kind of lull before the storm, a period when, as was customary, officers and staff summoned their wives and family to the seacoast town. Yamamoto was no different, although instead of his wife and family he sought the company of his longtime lover. Before arriving at Kure, he called Chiyoko in Tokyo to arrange for her to be with him. He had turned fifty-eight the previous month; Chiyoko was about to turn thirty-nine; they’d been together now for eight years, ever since their first summer of love in 1933. But the couple had to face a new hardship in addition to the already constant strain of separation that a war imposed on any relationship, familial or otherwise: Chiyoko had fallen ill, since mid-March suffering from pleurisy, an inflammation of the tissues surrounding the lungs, causing her severe chest pains and breathing difficulties. She had been receiving treatment, although at one point her doctors had worried that she might not recover. Of course, she longed to see Yamamoto, and she eagerly took his call “but hardly spoke by telephone due to much coughing,” she wrote in her diary. “Lost patience with tears.”
Even so, the couple made it happen. Though weakened, Chiyoko boarded an overnight train in Tokyo, accompanied by a doctor who administered injections of antibiotics. The next afternoon, May 14, Yamamoto waited in anticipation on the platform of the Kure station. He did not wear his uniform but was dressed in a disguise consisting of civilian clothes, glasses, and a mask—the kind of gauze mask worn over the nose and mouth to avoid spreading or inhaling germs. “My darling awaiting me,” Chiyoko wrote later. “I was wild with joy.” Yamamoto scooped up the depleted Chiyoko, put her onto his back, and carried her to a car waiting outside to take them to his hotel. “My thrilling body was carried in his arms,” she said. “Having difficulties in breathing, I had repeatedly been given injections, and it was only with this pain that I could be there.”
They spent four nights together at a hotel in Kure, with Yamamoto attending to his fragile lover. “Your spiritual strength in overcoming illness day by day is amazing indeed,” he told her afterward. Taking her to the train on the morning of her departure, Yamamoto watched from the platform and then reached up to take her hand through the window. Chiyoko later wrote, “Though I was so weak that I could not hold your hand strongly, you were very, very strong in holding my hands.” She felt a new pain—heartsickness—and did not want to bid him farewell. “I wished I could get off the train and remain beside you. When the train started to move, I hated to loose our firmly held hands.”
Yamamoto was likewise heartsick. His flagship left Kure and returned to the Hashirajima anchorage, the countdown to the Midway operation having begun in earnest. He poured out his feelings to Chiyoko—about war and love—in a May 27 letter written from Yamato. While she fought to regain her health, he said, he would “exert myself to fulfilling my duty for the country.” He even told her about Midway. “I will make an early sortie in the morning of the 29th to command the whole fleet at sea for about three weeks.” He also confessed that a part of him wanted none of it. “I wish, if I could, to desert everything in the world to live alone with you.” He ended his letter with a short verse pining for her, “with hot kisses on your lovely picture.” Chiyoko eventually recovered, and in the months to come Yamamoto continued to write and, on occasion, even called, but the four days and nights in Kure would turn out to be the last time they would be in each other’s arms.
JUST AS HE HAD SAID IN HIS LETTER, YAMAMOTO SET SAIL FROM the waters off Hiroshima on May 29, two days after Vice Admiral Nagumo’s fleet had departed—and nine days after Station Hypo code breaker Red Lasswell had decrypted a message detailing the Midway operation. The weather was clear starting out, and the atmosphere aboard Yamamoto’s flagship was upbeat, so much so that during the early going sailors belted out war songs. The further along they sailed, however, and as June 4 approached, a quiet tension set in. Yamamoto, manning the bridge, certainly appreciated the patriotic melodies, but his face was often grimacing in discomfort. Though nowhere near as ill as Chiyoko, he was struggling with his own health issues. He suffered shooting pains in his abdomen along with diarrhea, which was eventually diagnosed as worms.
It seemed to Yamamoto as he crossed the Pacific on the first of June that every part of the Midway plan was in place. One aspect had a smaller fleet that included another of the Imperial Navy’s aircraft carriers; it would attack the Aleutians. The barren, frozen islands were part of the United States’ Alaska territory; they were so remote that they had little strategic value except that whatever nation held them gained an edge in controlling northern Pacific transportation routes. Yamamoto and his planners were using the attack mainly as a diversion to pull the US Navy away from the main Midway operation—even if it defied the long-standing naval practice of concentrating sea power, not scattering it. Because Yamamoto had ended up dispersing his naval assets to such long distances, they would not be able to back each other. Then, in another bid to confuse the enemy as to the whereabouts of the Imperial Fleet, Yamamoto had instructed the radio communications staff to compose false messages making it seem as if the bulk of the Combined Fleet was training west of Japan in the Inland Sea. The trouble with all of that from Japan’s perspective, however, was the huge disadvantage it had in the shadow war of intelligence. Close to a hundred Japanese warships might be roaring toward Midway, but no amount of Japanese trickery mattered. Unknown to Yamamoto, his counterpart, Admiral Chester Nimitz, knew what was coming and had already patched together an opposing sea force.
As planned, Yamamoto’s attack force commander, Vice Admiral Nagumo, commenced the raid early on the morning of June 4. Nagumo ordered the launch of 108 planes—horizontal bombers and dive-bombers with Zero fighters as escorts—to attack and soften up Midway for a land invasion. But nothing went right. Nagumo was aboard his aircraft carrier, Akagi, positioned northwest of Midway, when his fleet found itself facing fighter planes coming at them from the United States’ Midway base. Nagumo’s forces managed to repulse the first US counterattack, but reality set in: instead of the Japanese fleet pummeling the US base with little resistance, the enemy was ready and waiting to do some pummeling of its own. Nagumo realized that he could not try landing ground troops yet and was urgently ordering a second aerial attack against the US base when new information arrived that turned everything upside down. A Japanese reconnaissance plane had discovered Nimitz’s warships on Nagumo’s left flank at a spot northeast of Midway known as Point Luck. The fleet included destroyers, cruisers, and, most surprising, three aircraft carriers, including Yorktown, outfitted with wooden braces to shore up its bulkheads. The Japanese had thought that Yorktown had been destroyed in the Coral Sea, but in fact it had been patched together at Pearl Harbor in time to join the US force at Midway.
The news was shocking. Yamamoto’s ultimate goal was to engage and crush the US carriers that had eluded the attack on Pearl Harbor in December, but the plan called for engagement to occur once the Midway attack was well under way, as the US carriers rushed to the scene. That three enemy carriers were already on location was off script—and Yamamoto’s Main Body was hundreds of miles away, nowhere close enough to help Nagumo. Minutes later, dozens of dive-bombers from the three US carriers began descending on Nagumo’s flagship, scoring direct hits that detonated the ship’s own bombs. The explosions rocked the Akagi, fires broke out, and black smoke spewed into the sky. “The scene was horrible to behold,” one officer later wrote. The devastation came swiftly and stunningly. That Akagi and the three other Japanese aircraft carriers were clustered so close together, never having expected any resistance, proved to be costly. They were easy targets.
Yamamoto’s face turned ashen as reports arrived from Nagumo’s staff. “Attacked by enemy land-based and carrier-based planes. Kaga, Soryu and Akagi ablaze,” one such report read. The messages came at a rapid-fire pace; in less than six minutes, Yamamoto learned that Kaga was hopelessly afire, Soryu was likewise engulfed in flames, and, stunningly, Nagumo was abandoning Akagi, escaping the flames by climbing through a window on the bridge. Nagumo transferred the attack force’s command post from the crippled Akagi to a light cruiser. He and his staff put their heads together in confusion and apprehension in the tiny bridge operations room. Yamamoto and the others had looks of “indescribable emptiness” in their eyes, a clerk on the Yamato later recalled. By late afternoon, both Kaga and Soryu were sunk, and not long afterward the carrier Hiryu was reported out of action. The four aircraft carriers that Yamamoto had committed to the Midway operation—ships that had been so central to his Imperial Fleet’s overall success to date—were gone. Yamamoto was notified that Nagumo’s flagship carrier, Akagi, though abandoned and listing, somehow remained afloat. Worried that the enemy might tow it back to the US mainland to show it off as a trophy, he made the agonizing decision to sink it. His staff protested the notion of torpedoing their own ship, but Yamamoto was insistent. “I’ll apologize to the Emperor myself.”
Yamamoto had a destroyer carry out the sinking of Akagi. He considered forging on and ordering Nagumo to stay in the fight, perhaps even land troops on Midway, in order to give the Main Body time to catch up. But then, reluctantly, he decided to call off the Midway operation. Without carriers to provide aerial support, he knew there was no chance of success. Japan’s naval forces began to withdraw and limp home. It was nearing midnight, less than twenty hours after fighting had begun—a nightmarish finish to a raid built on the high hopes for a decisive victory against the US fleet.
Japan’s largely uninterrupted expansion in the Pacific since the beginning of the year had been halted in its tracks. Yamamoto sternly ordered his staff not to criticize the Nagumo force. The mission’s failure, he said, was his responsibility. The Combined Fleet’s commander in chief retreated to his cabin, where he stayed for several days. A funereal silence fell over the Yamato. In the weeks to come, the Imperial Navy’s immediate challenge would be to rebuild its carrier arm. Beyond that, Yamamoto and the Japanese high command would turn their focus to the Solomon Islands, northeast of Australia, where they already had a stronghold at Rabaul on the island of New Britain. On June 7, Japanese troops made a landing on Guadalcanal, and in the wake of the massive setback at Midway, the decision was made to build an air base there. The thinking was that control of the Solomons would put the Japanese navy and army into a much stronger position to isolate Australia and disrupt any US plans to use it as a base.
IT WASN’T AS IF THE JAPANESE HADN’T INFLICTED DAMAGE AT Midway. The battle had been a bloodbath for both sides. For one thing, the Japanese had managed to finish off the carrier Yorktown, along with a US destroyer and 150 aircraft. But Nimitz’s outnumbered and outclassed forces had pulled off a David-versus-Goliath victory. Yamamoto had lost four carriers, the heavy cruiser Mikuma, and more than 240 aircraft. More than three thousand Japanese sailors and airmen had died, including many of his most experienced pilots and, just as important, many aircraft maintenance workers on the carriers that had sunk. Yamamoto and Japan’s military leaders were left to second-guess the plan, pick apart its execution, and find fault, but one game-changing factor lay beyond their awareness: the role of the US code breakers. Nimitz himself later wrote that “Midway was essentially a victory of intelligence.”
Few in Japan were told about Yamamoto’s loss at Midway, the grim truth suppressed in favor of propaganda aimed at maintaining the nation’s war fever and its veneer of invincibility. The nationalist press, loyal to Imperial General Headquarters, falsely claimed that the US fleet had lost two aircraft carriers and 150 planes to one of Japan’s cruisers and only 30 planes. “Navy Scores Another Epochal Victory” was one banner headline. To help keep lips sealed, most officers, sailors, and soldiers who’d served at Midway were immediately sent to different bases around the Pacific instead of being allowed to return home to be with their families, as was the usual custom.
The US media told quite a different story. “Jap Fleet Blasted in Midway Battle: Battleship and Carrier Damaged, Raid Repulsed,” screamed the front page of the Boston Globe. Every major daily newspaper in the United States carried similar headlines. “Pearl Harbor has now been partially avenged,” Admiral Nimitz asserted in a statement issued from his headquarters in Hawaii. “Vengeance will not be complete until Japanese sea power has been reduced to impotence.” One newspaper’s story gave US military leaders pause, however. The front page of the Chicago Tribune on June 7 had an article headlined “Navy Had Word of Jap Plan to Strike at Sea.” The article’s subhead went on to say that US officials had even known beforehand that Yamamoto’s move on the Aleutian Islands “was a feint.” The reporter who had written the scoop was war correspondent Stanley Johnston. It turned out that he had been aboard a transport ship returning from the Battle of the Coral Sea when he had gotten a look at the classified dispatch Nimitz had sent to commanders in the Pacific outlining Yamamoto’s plan to seize Midway. Johnston’s bombshell article was packed with specifics, saying that US naval officials had known which ships Yamamoto had deployed as well as his overall game plan: “It was known that the Japanese fleet—the most powerful yet used in this war—was broken into three sections: First, a striking force, next a support force, and finally an occupation force.”
Though the article did not say so explicitly, it certainly suggested that US code breakers had cracked the Japanese naval code. How else could Nimitz have known Yamamoto’s plans in advance? In Washington, the chief of naval operations, Admiral Ernest J. King, along with other top military officials, was livid, especially after other newspapers picked up the story. They pushed for a Justice Department leak investigation and possible charges of treason against the reporter and his editors under the Espionage Act of 1917.
The huge intelligence advantage provided by US code breakers suddenly seemed at risk. Washington held its collective breath, waiting for any sign that the Imperial Japanese Navy now realized that its code was compromised. One sure indication would be if Yamamoto’s Combined Fleet junked its JN-25 code system for an entirely new one, rather than following its usual practice of periodically modifying the JN-25. Japanese naval leaders, licking their wounds after Midway, were indeed suspicious. Yamamoto, for one, told Chiyoko that correspondence from the fleet had briefly been suspended, “as it is said that secrecy of the operations and movements seems to have been leaked out to the public and foreign countries.” But whether the Japanese somehow missed the newspaper article or whether out of hubris they could not imagine Americans being able to crack their code, the crisis passed. The Imperial Navy stuck with its basic JN-25 code system, and US officials detected no other evidence that the Japanese were onto the US code breaking. In the United States, a grand jury investigation was scuttled, in part to stop further public attention being given to the leak.
The glow of the Midway victory spread across the United States and especially to its forces all around the Pacific, including Fiji, where squadrons of Army Air Forces fighter pilots were training in waiting for their chance at combat. The pilots celebrated the news, with no one summarizing the triumphant moment better or more succinctly than did Captain John Mitchell. “We waxed the hell out of them,” he wrote Annie Lee the week after Midway, “and that’s just the beginning.”