7

Minazuki

Like the men in the submarines, the code breakers at Hypo were putting in thirty-hour shifts to accomplish their important work. Although they realized that the Benzedrine was causing side effects and health problems that could shorten their lives, they rationalized its use as necessary to getting the job done and almost certainly not as dangerous as facing bullets, shells, and depth charges. As Holmes would later write, “There is no justice in a war that sends one man to safe duty in a basement while thousands of his comrades are dying in desperate battle.”

Hypo’s chief, Joe Rochefort, and the chief intelligence officer for the Pacific Fleet, Edwin Layton, were especially aware of the intelligence failures leading to Pearl Harbor and vowed never to let it happen again. In the early months of 1942 they would confer with each other on a direct telephone line up to forty times a day. To ensure security, the phone wasn’t even wired into the switchboard system and relied on a hand-crank magneto to make it ring.

Rochefort’s team started to break through the JN-25 code in earnest. Each decrypt—though incomplete—added tantalizing clues about the Japanese navy’s capabilities, movements, and plans. It was like reading the enemy’s mind, but with every third or fourth word blanked out. When the same string of five numbers cropped up in multiple radio intercepts, the code breakers had to rely on their photographic memories to recall certain instances where they’d last seen that five-digit code, as well as its context, in order to infer what that code meant. Sometimes the last use of those five numbers had occurred days, weeks, or even months ago. Luckily as the Japanese kicked their complicated offensive operations into high gear, the code breakers had more than enough examples to start making sense of how the Naval General Staff and the Combined Fleet were moving the Japanese navy across the vast chessboard of the Pacific. The Naval General Staff was roughly analogous to the U.S. Navy Department, and the Combined Fleet under Admiral Isoroku Yamamoto was the counterpart to the American Pacific Fleet under Admiral Chester Nimitz.

With a staff of only about fifty men, Rochefort’s team started by prioritizing the messages; obviously a message from a task force commander promised better information than the message of a supply ship skipper. Then the cryptographers stripped the messages of additives. The ex–USS California band members began the laborious process of hand-punching the tabulator cards for the IBM machines, while Tom Dyer’s assistant Ham Wright supervised the machine’s operation twenty-four hours a day. Most messages took about sixty or seventy punch cards, sometimes more.

The resulting code groups—the strings of five-digit numbers stripped of their additive numbers—would go to cryptographer/linguists, the most specialized and highly trained of the lot. These included Rochefort and his assistant Dyer, as well as Joseph Finnegan and Alva Lasswell. All had attended Japanese language instruction in Japan and had special abilities for the task, which, as Layton put it, was like putting a puzzle together without all the pieces. Finnegan was an intuitive code breaker who made broad, but calculated and logical, leaps based on the associations of disparate messages, whereas Lasswell made meticulous and conservative estimations drawn only from what could be demonstrated. Rochefort recognized a good pairing when he saw one, and as Holmes recounted, when Finnegan had an impressive hunch, Rochefort would pretend not to believe him. Finnegan would then enlist Lasswell’s complementary skills to fill in the gaps between what seemed to be Finnegan’s flights of fancy. The result was an inspired, but solid, intelligence product. Even this result had gaps, however, and Rochefort and Dyer would spend hours trying to fill in blanks for 100 to 150 messages a day. The result of several hours on one message that had seemed at first to be a major breakthrough might eventually reveal itself to be only a mundane report about the water supply on some godforsaken coral outpost in the middle of nowhere. But even that new information was grist for the mill, useful in that its codes were no longer unknown entities; Rochefort’s exquisitely compartmentalized mind would file it away for possible use someday.

Finnegan learned that the Japanese radio operators on newly captured Wake Island in the Central Pacific were recording American call signs to analyze radio traffic between the U.S. Navy’s ships and outposts, as well as listening to commercial broadcasts from Honolulu for possible intelligence information. Since this represented an opportunity to compare the Japanese reports of what the Americans were broadcasting, if Finnegan could get his hands on broadcast transcripts he might be able to identify several valuable code groups. Holmes had recently transferred his plotting duties to other offices in the Navy Yard and had taken on whatever administrative tasks would lighten Rochefort’s load, so he volunteered to try to get transcripts of the Honolulu broadcasts. Unfortunately, he discovered that the radio stations didn’t keep such records. Stumped, Finnegan reasoned that the broadcasts were based on reporting from the local newspapers, and asked for a complete copy of both local news-papers since December 7.

Rochefort also learned about the Kamikawa Maru—a seaplane tender or mother ship that could launch and service several seaplanes—located around the Woodlark Island area that Holmes had decoded. This suggested that the Japanese were conducting reconnaissance in the 500-mile radius of the seaplane tender and setting up for an offensive action. Finnegan discovered the presence of a new mystery ship he dubbed the “Ryukaku” based on the information he had available. It had land-based planes associated with it instead of seaplanes, and they surmised that it was a new, smaller aircraft carrier capable of supporting invasions. As more pieces of the puzzle dribbled in, they came to find out that the Japanese navy’s Fourth Fleet—a collection of cruisers and destroyers suitable for protecting a landing operation—was assembling in Rabaul, a Japanese stronghold that was within striking distance of northeastern Australia, the Solomon Islands, and New Guinea. The kicker came when they started getting traffic about a geographical location code-named “MO.”

The Japanese code names followed a pattern—Rabaul was “RR,” and the code names for the islands around Rabaul started with R; Palau was “PP”, and its associated islands began with P. Rochefort guessed that the Japanese were assembling an invasion fleet to take Port Moresby—MO—on Papua New Guinea and perhaps establishing new bases farther into the Pacific in order to cut off and invade Australia. Thus advised, Admiral Nimitz and Layton realized that if they were able to get a task force down to thwart the invasion of Port Moresby, not only would they save Australia from the encroaching Japanese stranglehold, but they might be able to isolate part of the Kido Butai’s carrier force and defeat it in detail.

For their part, the Japanese offensive plan for the war had gone off so successfully and with so few losses that they were scrambling to determine what to do next. Although they knew there would be much fighting ahead, with their initial missions accomplished, a triumphal mentality set in that would become known as “shōribyō,” or victory disease. The Naval General Staff in Tokyo made plans to invade Australia, but dropped the idea when it became clear that the Japanese army wouldn’t spring ten divisions from the occupation of Manchuria. So they developed more modest plans to invade New Guinea, Fiji, New Caledonia, and the Solomons, starting with Port Moresby, where they could set up bases to raid convoys supplying Australia and stage long-range bombing patrols on enemy warships and the Australian mainland.

In contrast, the Combined Fleet officers’ priority was to create a ring of mutually supporting defensive positions out of the various island chains—unsinkable aircraft carriers—spread throughout the vast ocean. Their argument was that concentrating naval power in the south would leave the Japanese mainland open to carrier raids from the central and barren North Pacific—just as they had attacked Pearl Harbor. But if the Japanese were able to make a base in the Aleutians and take Midway Island, then Oahu, they would rule the Pacific. Since the Combined Fleet’s planners had gained almost insurmountable credibility with the raid on Pearl Harbor, the Naval General Staff acceded to their demands. The seeming necessity for taking Midway was punctuated with new urgency when Captain Jimmy Doolittle led his famous bomber raid on Tokyo and other parts of the Japanese mainland on April 18, 1942. When FDR was asked whether the bombers came from an island in the Pacific or from mainland China, he merely answered “Shangri-La.” But Doolittle’s ordinarily land-based B-25 bombers had taken off from the aircraft carrier Hornet in a task force led by Admiral William “Bull” Halsey hundreds of miles from the Japanese coastline.

The Japanese public was shocked that American bombers could somehow reach across thousands of miles, and that the Americans would have the audacity to make war on their sacred homeland. Even though the raid destroyed little of Japan’s war-making infrastructure, the effects loomed far out of proportion. The supremely confident militarists had egg on their face, and took steps to recall pilots and their airplanes back to the homeland. All available Japanese navy ships went on a wild-goose chase for the carriers, burning precious fuel and wasting valuable time. The raid also had the effect of making the high command shift resources away from where they would be most valuable, and delayed their other offensive operations, which gave the Americans invaluable breathing space. During this time, the Kido Butai was occupied with British targets in the Indian Ocean, and Nimitz’s carriers Enterprise and Lexington were able to stage hit-and-run raids against the Marshall Islands with relative impunity. This caused much consternation among the upper echelons of the Japanese navy, upsetting their offensive plans even further.

Rochefort now told Layton that after the Kido Butai’s successful Indian Ocean campaign, the aircraft carriers Shokaku and Zuikaku would be going to Truk instead of Japan. This suggested that after becoming aware of the presence of Enterprise and Lexington in the Marshalls, the Japanese might reinforce the MO invasion force and its escort carrier “Ryukaku” with the Shokaku and Zuikaku. The odds then would be against the Americans three to two. For a force with a total of four aircraft carriers in the Pacific^* versus an estimated eight for the Japanese, the loss of even one aircraft carrier would be a serious blow. But the Allies couldn’t afford to lose Port Moresby or let the Japanese control shipping to Australia, and so the stage was set for the historic Battle of the Coral Sea. The tidings for the Americans were not good the night before battle as they received a radio transmission from the U.S. Navy radiomen in Corregidor:

ONE HUNDRED AND SEVENTY-THREE OFFICERS AND TWENTY-THREE HUNDRED AND SEVENTEEN MEN OF THE NAVY REAFFIRM THEIR LOYALTY AND DEVOTION TO COUNTRY, FAMILIES, AND FRIENDS.

It was Corregidor’s final transmission before the Philippines finally capitulated to the Japanese.

If the stakes hadn’t been so high, the Battle of the Coral Sea would have been characterized as a comedy of errors. The U.S. task force commander Vice Admiral Frank Jack Fletcher chased false leads, split up his forces, and repeatedly ignored the radio intelligence officer on board his own ship. When a reconnaissance plane gave a contact report with a faulty code, Fletcher prematurely launched all the aircraft from his two carriers, Yorktown and Lexington. If Japanese land- or carrier-based planes found them, they would have no defense. When Fletcher discov-ered the error, he flew into a rage. Luckily, MacArthur’s bombers reported a carrier sighting not far off from the original contact report, and Fletcher broke radio silence to redirect them to the new coordinates. They found and sank the “Ryukaku”—in actuality, the smaller escort carrier Shoho—and triumphantly radioed, “Scratch one flattop!” For their part, the Japanese had no radio intelligence to speak of, and although they were nearly within striking distance of the American carriers, their reconnaissance flights were hampered by a fortuitous rainsquall that appeared between the forces. Fletcher’s radio intelligence officer told him exactly where he’d find the Shokaku and Zuikaku, but Fletcher refused to believe him until Japanese planes bombed into oblivion an oiler and destroyer that Fletcher had left behind. Rear Admiral Chuichi Hara, the Japanese commander of Carrier Division Five, discovered Fletcher’s location from the destruction of the Shoho and later by a floatplane report. After expending all their bombs on the hapless American oiler and destroyer, Hara’s planes harmlessly circled the Yorktown and Lexington for a friendly visit. After returning from the attack on the Shoho, the planes of the Yorktown and Lexington refueled and rearmed. Inexplicably, despite the fact that both Fletcher and Hara had a very good idea of where the other was, neither launched an attack until the next morning.

Hara’s planes made an attack on both the Lexington and the Yorktown. The “Lady Lex” was older, larger, and less maneuverable, and the Japanese bombers found their mark as the Lexington slowly turned to evade the bombs. The Yorktown was also heavily damaged, but the Lexington had so many fires that sections of its inch-thick plating actually glowed cherry red in the noonday sun. To keep her from the Japanese, Fletcher sank the ship with torpedoes launched by a destroyer. The Japanese were luckier, but not by much. Although the Shokaku and Zuikaku survived the battle, they were both so damaged that they would need extensive repairs, keeping them out of action for months.

At the outset, it looked as though the Japanese had won yet again, but this time the margins were closer. They had exchanged the smaller escort carrier Shoho for the heavy carrier Lexington. For a navy with an estimated carrier superiority of ten to four, the results favored the Japanese.

There were other, more important developments that threatened the United States fleet, however. The Australian prime minister received Hypo’s weekly intelligence summaries through the Australian navy’s coordination with the Americans. In an effort to quell the fear of a Japanese invasion, he prematurely announced that the invasion of Port Moresby had been called off, and that Australia would have plenty of warning if the Japanese attempted another invasion. How he could have known this so soon after the battle came perilously close to leaking Hypo’s secrets. With an inferior naval force, Nimitz and the Allies had only their superior intelligence to avoid catastrophic ambushes and forewarning of invasions, and if the ill-timed words aroused any suspicion that the Japanese code was compromised, now or in the future, it would likely have changed the outcome of the war.

Although the Battle of the Coral Sea didn’t seem like a victory at the time, the results turned out to be advantageous for the Americans. The Shokaku was so damaged as to be put out of action for several months—long enough for the Americans to get some breathing space after so many defeats. In addition, a large number of the Zuikaku’s highly trained and battle-hardened pilots, as well as their planes, were now lost forever, making that ship ineffective until it could get replacements. Another benefit of the Coral Sea engagement was that the Japanese flooded the airwaves with messages encoded in JN-25, which gave Hypo, the Cast team relocated to Melbourne, and Negat in Washington, more examples of the code than they could reasonably handle. More important, it gave Nimitz the confidence he needed to trust the radio intelligence he was getting from Layton, and by extension Joe Rochefort. This confidence would be crucial in the month to come, when on May 11, Rochefort discovered that the Japanese were assembling a massive armada in Saipan. The message specified particular anchorages for the Japanese Second Fleet. Two days later, the term “MI” was associated with an invasion force. The day after that, logistical details turned up when the Japanese navy authorized maps of the Hawaiian Islands chain to be sent to Saipan, as well as another message describing a Koryaku Butai—invasion force—participating in a forthcoming “AF” campaign. From what they could gather, AF served as a submarine base that sent out long-range reconnaissance patrols. This suggested Pearl; Midway, west of Pearl; or Johnston Island, southwest of Pearl. Rochefort also noted messages about the Aleutian Islands chain off Alaska, specifically Attu, Kiska, and Dutch Harbor. Rochefort was convinced that Yamamoto was building up a fantastically elaborate operation, and that the main target was Midway Island.

Back in Washington, Navy Department head Admiral Ernest King expressed doubts, and wanted Nimitz to have Halsey cover the southwest Pacific area in the event that the Japanese continued with their intentions to threaten Australia by taking Fiji, Samoa, and New Caledonia. King was being advised by the ambitious Redman brothers, Joseph and John, who had restructured OP-20-G, the department overseeing the code breakers at Negat, Hypo, and Cast.* As Hypo was part of their fiefdom, they wanted Rochefort to conform to nice organizational charts and do as he was instructed, regardless of whether that marshaled his—or Hypo’s—considerable talents in the most productive way. Their bureaucratic reorganization scheme had its merits in that it geared up OP-20-G to produce intelligence on a massive wartime scale, but it shunted aside Laurance Safford, one of the Navy’s most gifted cryptographers. It also severed several informal personal connections between Negat and Hypo, causing friction and morale problems. The most serious problem was that without Safford, Negat started to misinterpret the radio intelligence about whether AF was Midway.

One of Negat’s objections was that it was entirely too coincidental that the Japanese code for Midway—AF—was suspiciously similar to the Americans’. When they read a Rochefort report that a Japanese unit had requested that their mail be forwarded to their new address at Midway, Negat suggested that Rochefort was falling for Japanese deception and misinformation. They claimed that the A in AF stood for the Aleutians. Then they said it might be Australia. To cover all their bases, they started warning that the West Coast might be the target. With recriminations about the Pearl Harbor disaster running rampant, Admiral King had a knee-jerk reaction to every possible threat, no matter how negligible, and sent Nimitz scrambling with several attack warnings. In addition to the backbreaking work of trying to crack enough of JN-25 to confirm that AF was Midway, determine the Japanese order of battle, and discover when and where they would attack, Rochefort had to do the painstaking task of going over Negat’s many mistakes and misinterpretations to determine where their solutions had gone wrong. The disagreements ignited in what could be called a 1940s flame war until someone pointed out the errors to Admiral King and he finally conceded that AF was Midway. The younger Redman was doubtless humiliated to have his competence called into question. Undaunted, Negat and the Redmans then insisted that the Midway invasion was most likely scheduled for mid-June, and proceeded to fight tooth and nail over that interpretation.

But it was Nimitz’s call, and according to Layton, he was convinced that Rochefort was right from May 14 onward. The problem was that if Rochefort were right, then Negat—and Nimitz’s superior, King—were wrong. Nimitz had to find a way to get Halsey’s task force back to Hawaii for the Midway battle, which was coming soon. Nimitz relied on sleight-of-hand, and sent an “eyes only” message to Halsey hinting that he should somehow get sighted on a course toward Ocean and Noumea islands, where the Japanese were planning an invasion. A seaplane spotted the task force, Halsey got clean away, and once more the Japanese got the jitters about their invasion plans for Ocean and Noumea in New Caledonia, off the Coral Sea.

Rochefort was able to confirm all of this by radio interception and decryption.

Since the invasion plans for Ocean and Noumea were now off, and King was finally convinced that Midway was the new target—albeit at a much later time—Nimitz was able to convince King to bring Halsey’s carriers back to Pearl in time for the Midway invasion. Incredibly, Negat backtracked and started making more ominous warnings that AF may yet be a target in Alaska. Rochefort knew that the Aleutians were also a target, and that to head off any more interference from Washington he needed to prove beyond doubt that AF was Midway. A massive Japanese task force was heading to one of America’s last Pacific outposts while bureaucrats in Washington dithered with inconsequential, vague, and contradictory intelligence assessments.

At this time, Rochefort, Holmes, Finnegan, and Dyer were discussing the Midway problem around one of the Hypo desks when Holmes offhandedly remarked that he’d gone there while he was teaching engineering at the University of Hawaii. They’d done studies to determine what effect saltwater had on mixing concrete for the buildings there, since they made all their precious fresh water with massive evaporation tanks. If the evaporators broke down, there would be serious problems. Finnegan caught on to this and said that if the Japanese knew there were problems with the fresh water evaporators, their listening post on Wake Island would be sure to report it. Rochefort sat there quietly, the permutations of code groups clicking away in his mind as he reached back to the code groups they’d broken. Water, he thought. Midway. AF.

“That’s all right, Joe,” he said to Finnegan. He got up and left. Holmes wouldn’t learn until years later that the thousands of tumblers in Rochefort’s mind clicked in unison at that moment and unlocked the key to proving AF’s identity.

In the succeeding days, they got bits and bobs of tantalizing information. Admiral Chuichi Nagumo would lead the Kido Butai to be in position northwest of AF by N-2 day for the attack on N-day. What was N-day? they wondered. From their many decrypts, they had only three examples of how the Japanese coded dates: three kana characters. This was further encrypted beyond the additives and codes. It was truly a riddle wrapped in a mystery inside an enigma. Rochefort’s group realized that in order to get all the dates to snap into place, they would have to solve this riddle.

While they were working the date-time code, Yamamoto flashed the Combined Fleet’s order of battle—the roster of ships he intended to use—as well as detailed instructions for the campaign against AF and the Aleutians. Finnegan recognized it for what it was straightaway and started to decode it with help from Ham Wright and Joe Rochefort. That left Lasswell with the date-month code.

Amid all the piles of intel, a decrypt came across Tom Dyer’s desk from the Japanese stronghold of Kwajalein:

The AF air unit sent following radio message to commandant 14th Naval district. AK (Pearl Harbor) of 20th. With reference to this unit’s report dated 19th. At present time we have only enough water for two weeks. Please supply us immediately.

Dyer correctly interpreted that Midway—AF—had sent a plain-language message to Admiral Bloch at Pearl Harbor—AK—thereby giving the Japanese vital information. He snorted and waved the message at Rochefort. “Those stupid bastards on Midway. What do they ever mean by sending out a message like this in plain language?”

Rochefort was uncharacteristically placid about the affair because it was a devious bit of radio intelligence deception he’d played—not only on the Japanese but also on Washington. The ruse wouldn’t be revealed for years, but when Holmes had remembered the water distillers on Midway, and that Finnegan was reading Japanese intelligence reports out of Wake, Rochefort realized that he knew enough of JN-25 to get the Japanese to inadvertently show their hand. There was at that time an underwater cable between Hawaii and Midway for secure communications. He asked for, and received, permission to send a message over the secure line to Midway requesting that they send a plain-language radio broadcast stating that their water distillers had broken. They elaborated by also sending it in a strip-cipher code that was known to have been captured at Wake Island. Bloch kept the deception going by acknowledging receipt and saying that he’d send barges with fresh water. The Japanese were listening, too, of course, wrote a coded report, and sent it out—thereby conclusively confirming that AF was Midway. Rochefort—and likely Bloch, Layton, and Nimitz—kept the secret for years.

For their part, Washington warned Rochefort not to be taken in by Japanese radio deception.

On May 25, the Japanese changed the additive tables for JN-25, just as they had before their last major offensive, Pearl Harbor. It was a blow for Hypo and the rest of the code breakers, but by that time Finnegan, Wright, and Rochefort had decoded 90 percent of Yamamoto’s May 20 directive. After the Combined Fleet assembled at Saipan, the commanders would parley on May 26 and depart for their destination on May 27. Given the distances involved and the speed they would travel, it would put the massive Japanese armada close to Midway by June 1 or June 2.

Late on May 26, Lasswell finally made a breakthrough on the date code: It was a simple grid with the twelve months listed as columns and thirty-one kana characters as rows, with alternating kana characters in the cross references providing a garble check. Having solved the all-important date code, Hypo could reread the many decrypts about the invasion plans within the context of when the invasion would happen. The Japanese decreed that the battle for Midway would occur on the second or third day of Minazuki, the “low water month” of June. It was also apparently the code name for their anticipated new mailing address.

Rochefort worked around the clock to make sure everything checked out; he had a meeting the next morning with Nimitz, Layton, and the top commanders of the Pacific Fleet. He was fully aware that the Pacific command would be setting sail on his advice and would make momentous decisions based on his assemblage of details great and small. If he misinterpreted even a small aspect of the jumbled pile of decrypted messages scattered on his desk and throughout the basement, the task force commanders could easily make mistakes that would cost lives, ships, maybe even the war. There were no second chances. Running late, Rochefort put on his coat and hat, tucked some charts and papers under his elbow, and ran out the door for the most important meeting of his life.

Nimitz’s ordinarily bright blue eyes fixed on him with withering disapproval. Rochefort was late, disheveled, and unshaved, shifting uneasily before the assembled group of high-ranking Navy officials. Exhausted, Rochefort peered at them with bloodshot eyes; he could see that was more than enough scrambled eggs for a buffet, and that everyone was cleared for what he was about to divulge.

He told them that the Japanese would attack Alaska, and although they intended to keep the Aleutian Islands strongholds, that the timing was a ruse to lure the Pacific Fleet. At Midway, the fleet could expect to face the first and second carrier divisions, including the Kido Butai’s Akagi, Kaga, Soryu, and Hiryu, along with elements of other fleets as escorts, and a main body invasion force. The Shokaku and Zuikaku would not be there due to the damage they received at the Battle of the Coral Sea. The Japanese had sortied from Saipan that very day and would attack Midway from the northwest on June 2 or 3 to soften up the island for the invasion force that would follow. The staff marveled at the value of what he was telling them; Nimitz asked some questions, including those about the source, to which Rochefort replied that the source was very good. One of the men gathered there commented that Rochefort’s spy in Tokyo was worth every penny, but neither Rochefort, Layton, nor Nimitz tried to dissuade him from believing that the intelligence came from a mole in the enemy’s camp.

After the meeting, Nimitz famously asked Layton for his opinion on where and when they would find the Kido Butai. Layton demurred, saying that it wasn’t possible to give a precise location or time, but Nimitz insisted. As Layton recalled later in his book, “I knew that I would have to stick my neck out, but that was clearly what he wanted. Summarizing all my data, I told Nimitz that the carriers would probably attack on the morning of 4 June, from the northwest on a bearing of 325 degrees. They could be sighted at about 175 miles from Midway at around 0700 local time.”

For Nimitz, there was never any question about what to do. Thousands of miles southwest of Pearl, the Tangier and the Salt Lake City started to send radio broadcasts intended to resemble carrier task forces. On May 28 the carriers Enterprise and Hornet steamed out of Pearl for a point 350 miles northeast of Midway to ambush the Kido Butai, while all available dockworkers worked night and day to shore up and repair the crippled Yorktown. While the rest of Honolulu was blacked out, the oxyacetylene torches and arc welders swarming over the ship cast a weird glow across the nighttime harbor. The workmen used so much electricity trying to cram three months of repairs into three days that blackouts were reported across the island. Where the workmen couldn’t make structural iron repairs in the bombed-out ship, they shored up plates and bulkheads with ordinary lumber. They simply had to do everything in their power to get the ship back into fighting order; even if they repaired the ship in time, the odds would be three to four in favor of the Japanese. If the Shokaku and Zuikaku hadn’t been knocked out of commission at the Coral Sea, the Kido Butai would have been invincible. As it was, with the element of surprise provided only by Hypo, Nimitz’s task force commanders had a good chance of winning an upset victory. Whatever the outcome, Nimitz appreciated that this was perhaps the most momentous battle of the war, and may well decide the war’s outcome. It was arguably the most important naval battle in history, and it would be determined by Joe Rochefort and the group at Hypo.

Miraculously, the dockworkers repaired Yorktown enough for it to accompany the other two carriers. It left Pearl Harbor on Saturday, May 30, and not a day too soon. Japanese submarines arrived on that day to form a reconnaissance picket around the Hawaiian Islands to report aircraft carriers and attack targets of opportunity. Their arrival had been delayed by the hasty redrawing of plans caused by the Coral Sea battle, Doolittle’s bombing of Tokyo, and raids on Japanese strongholds in the Pacific. Had they gotten there in time to report the carriers, Nimitz would have lost the element of surprise. An intelligence coup also prevented Japanese plans for a reconnaissance flight over Pearl before the battle. Nimitz’s forces escaped detection by the very narrowest of margins, but the Japanese had one last chance to discover the ambush. Somehow a Japanese radio intelligence unit at Owada in Japan discovered that there were carriers in the Hawaiian area—not in the southwest Pacific as they had previously assumed. They transmitted their intelligence to Yamamoto’s flagship in the main force, the Yamato, as well as to Admiral Nagumo, who was commanding the four carriers in the Kido Butai. Nagumo never received the report, and Yamamoto refused to break radio silence to amplify the warning; he assumed that Nagumo had received it and read it. Nagumo’s first confirmation of the presence of American carriers would come at a time when he would be least able to do anything about it.

The battle started when a U.S. Navy PBY flying boat located the invasion fleet and radioed a report. Nimitz reiterated to his task force commanders that the invasion fleet was not the striking force with the Kido Butai’s estimated four or five carriers. The next day, Nagumo launched an attack on Midway with nearly all his planes. The ground-based forces on Midway mustered up some bombers to locate and attack the Japanese carriers, but they were ineffective. Midway’s obsolete fighter planes were likewise swatted from the sky, although the antiaircraft guns made a good account of themselves and shot down several of the attacking Japanese planes. After assessing the effectiveness of their attack on the island, the Japanese flight commanders recommended that they come back to finish off the job.

While the Japanese were returning from bombing Midway, task force commanders Admirals Fletcher and Raymond A. Spruance launched their own attacks—and their timing couldn’t have been better. Although the Japanese had learned of one American carrier through a floatplane reconnaissance report, they didn’t have nearly as much information as Fletcher and Spruance. Nagumo was caught on the horns of a dilemma: His pilots were low on fuel and he’d already started outfitting a second wave with bombs suitable for attacks on land targets. He was committed to getting the pilots back, then wasted precious time refitting the available planes with ordnance to go after the one carrier they knew about. Then they spotted the first American torpedo bomber.

The top-of-the-line Japanese Zero fighter planes made quick work of the obsolete American Devastator planes as they came in flat and slow in order to launch their torpedoes. Of forty-one such planes launched in the raid, only four would come back, and of the thirty-seven crews who were shot down, only one man survived. Despite the signal failure to damage even a single Japanese ship, the torpedo bombers had accomplished at least one thing: The Zeroes were now low to the water and would not be able to gain sufficient altitude in time to have an effect on the American dive bombers, which came in squadron by squadron to drop a series of devastating bombs on the Soryu, the Kaga, and the Akagi. Only the Hiryu escaped unscathed to launch its own attack on the American carriers. Each of the Japanese carriers that had been hit were doomed because they received the bomb hits when their hangars were filled with highly inflammable aviation fuel and munitions. The remaining pilots from these ships landed on the Hiryu as its own pilots searched for the American carriers and found the Yorktown.

The hastily repaired veteran of the Coral Sea battle took several hits and lost power. The order to abandon ship went over the PA system, and the crew made its escape. When the stubborn old carrier didn’t sink, some crewmen went back to see if it could be saved and started to pump some of the seawater out of the bilge. But no one could account for the I-168, a Japanese submarine lurking off the slow-moving carrier. A salvo of four torpedoes blew new holes into the Yorktown and sank the destroyer assisting her. With the massive amounts of new water cascading into the ship, and the loss of the pump power from the destroyer, she finally sank.

The sorties from the remaining carriers, Hornet and Enterprise, found and sank the final Japanese carrier, Hiryu, and with it the last of Japan’s most seasoned naval pilots. The defeat was so surprising, so total, that it threw Yamamoto and the rest of the Japanese invasion forces into disarray. After a few feints to try to draw Spruance toward the Combined Fleet’s battleships in a night engagement Spruance was sure to lose, Yamamoto conceded defeat and called off the invasion. He turned back the mighty Combined Fleet—an armada whose cumulative deck area was larger than the twenty acres of the island they’d been sent to capture.

Despite the fact that many of their officers realized the proportions of their defeat, for the Japanese, their case of victory disease acquired peculiar symptoms. Speaking through their propaganda organs, Midway and every other defeat was either downplayed or became a victory, and by some strange logic the massacre of thousands of their troops and sailors became signs of progress. The state of the armed forces was strong—and getting stronger. Pilots claiming to have shot down a plane and skippers claiming to sink an American ship were given credit for cumulatively sinking whole American armadas, even on the scantest of evidence. Victory would only take more time—and more sacrifice. As loss after loss piled up and the traditional wooden boxes containing the cremated remains of fallen sailors and soldiers came home, many refused to acknowledge the inevitability of defeat. Even later when Japan’s major cities were firebombed into cinders, wide swaths of the population still thought that they were winning the war, because that was what they were told by their leaders. Toward the end of the war, the many Japanese who read the writing on the wall had to consider whether national defeat might be preferable to the peculiar present state of starving in supposed victory.

The U.S. Navy was ecstatic. When the location of the Japanese carriers came through to Nimitz, he recalled Layton’s prediction of where and when they would find them, and told him, “Well, you were only five minutes, five degrees, and five miles out.” Although they were down to three carriers in the Pacific—the Hornet and the Enterprise, along with the Saratoga, which was being refitted on the West Coast—they had destroyed four of Japan’s six largest aircraft carriers and rendered the other two incapable of fighting. The Japanese navy could no longer range around the Pacific and project its power at will. The American public was heartened to have good news after so many months of defeat and retreat, but just as they’d wondered where Pearl Harbor was on December 7, 1941, they puzzled at the significance of the flyspeck of Midway on a map of the Pacific and wondered how the Navy had conducted a major naval engagement without any of the ships actually spotting one another.

Unfortunately a Chicago Tribune reporter with special knowledge of Navy operations thought everyone should know more. His front-page headline was a huge scoop, straight out of the Navy’s hide:

JAP FLEET SMASHED BY U.S.—
2 CARRIERS SUNK AT MIDWAY

Navy Had Word of Jap Plan to Strike at Sea—

Knew Dutch Harbor Was a Feint

The article went on to describe the Japanese ships in such detail that the only logical conclusion was that the Americans knew about the invasions at Midway and the Aleutians because they had broken the enemy’s code. Japanese naval attachés at neutral consulates and embassies around the world read American publications for intelligence—and this was a whopper. It was only the first of a string of security breaches, near misses, and self-inflicted wounds that would plague the Navy well into the next year.