Codebreakers Victory (26 page)

The Doolittle raid had a much more important consequence than that of its bombs. In those early days of 1942 the Japanese high command, flush with victory, was debating its next offensive strategies. One group wanted to parlay the capture of Rabaul into the seizure of Port Moresby, on the south coast of the huge island of New Guinea, which hangs over Australia in the north like a giant incubus. Port Moresby was only a short hop across the Coral Sea to the Australian mainland. The group also advocated conquests in the Solomon Islands and beyond to sever Australia's links with the U.S.

Admiral Yamamoto pressed for an alternative plan. He wanted to extend the Coprosperity Sphere in the other direction: to establish a new perimeter that included the Aleutian Islands in the north and Midway Island on the eastern sea frontier. He argued that his strategy would lead to eliminating U.S. power in the Pacific in two ways. The capture of Midway would provide a base for the conquest of Hawaii. And the need for the U.S. to defend the island would draw the battered Pacific Fleet into deep water where he could complete the decisive battle he had started at Pearl Harbor.

The Decisive Battle was an important concept to Japanese sea lords, as John Prados emphasized in his book
Combined Fleet Decoded.
"The Japanese fleet," he wrote, "was built to engage in the Decisive Battle, trained to conduct it, and officers and men were imbued with the idea of the Decisive Battle almost as a tradition, an ideology, a cult." The pervasive idea traced back to the Japanese victory over Russia in the 1904 battle at Tsushima. Russia had put together a fleet in European waters and then sent it halfway around the world to engage the Japanese. Because of the long journey and a variety of tribulations along the way, the Russians had arrived in the Far East thoroughly dispirited, and they were soundly defeated. Just so, Yamamoto believed, could Japan humble the U.S. Navy. In traversing the vast distances of the Pacific, the American fleet could be harried, weakened and confused by submarine torpedo attacks, destroyer flotillas and aircraft strikes. Then the concentrated power of the Imperial Navy could fall on it and deliver the deathblow.

The loss of Midway, the seizures in the Aleutians and the annihilation of the U.S. fleet, Yamamoto stressed, would dishearten the American people. The admiral again held out the prospect of a negotiated peace on terms dictated by Japan.

Doolittle's raid swept away any resistance to Yamamoto's plan. As he himself commented, "Even though there wasn't much damage, it's a disgrace that the skies over the Imperial Palace should have been defiled without a single enemy plane shot down." It must not happen again. Midway was near enough to serve as a launching site for similar attacks in the future, and the Dutch Harbor base in the western Aleutians was also too close for comfort. The army, which had heretofore refused to participate in the admiral's scheme, now insisted on becoming a part of it.

Japan's military leadership, basking in the knowledge that their losses had been far less than anticipated, decided it was unnecessary to choose between the alternatives. They could do both: carry out the drive against Port Moresby while also proceeding with the Midway-Aleutians campaign.

 

 

Winning the Battle of the Coral Sea

 

Rebuffing the Japanese commanders' first attempt to take Port Moresby was primarily the task of the U.S. Navy. Rochefort's team informed Admiral Nimitz of the great flotilla of Japanese warships that were escorting transports carrying a whole division of invasion troops, heading down from Rabaul. The Japanese objectives were to capture Tulagi, one of the Solomon Islands, and build an airfield there while also entering the Coral Sea to seize Port Moresby.

In his memoir, Layton emphasized that Nimitz's entire Coral Sea operation was guided by Rochefort's "sixth sense" in assembling seemingly unrelated information in partially decrypted enemy messages and turning the puzzle into an accurate picture of enemy intentions.

Believing his codebreakers, Nimitz evacuated the small Australian detachment at Tulagi before the Japanese invaders arrived. He also relied on advice from decodes to station his ships to the best advantage in the Coral Sea.

Vice Admiral Shigeyoshi Inouye, commanding the Japanese fleet, was expecting that his passage would prove a surprise to the Allies. His shock was great, therefore, when U.S. carrier-based planes began to attack and sink his ships.

The Battle of the Coral Sea, fought from May 4 to May 8, 1942, was a mix of poor judgment, faulty leadership, missed opportunities and lucky hits on both sides. Admiral Morison thought it might better be called "the Battle of Naval Errors," but he also wrote, "It was an indispensable preliminary to the great victory of Midway."

For the U.S., a prime opportunity was lost when one of Nimitz's commanders, Vice Admiral Jack Fletcher, became antagonistic toward the mobile intelligence unit aboard his flagship and turned a deaf ear to them. What had miffed him was that when he had asked the unit's leader to describe his work to a wardroom of officers, the leader's consciousness of his security restraints had caused him to refuse. Consequently, when the unit pinpointed the location of nearby Japanese carriers and revealed that they were in the vulnerable stage of refueling aircraft, Fletcher, still piqued, declined to act on the information.

In the end, the U.S. traded the sinking of a Japanese light carrier and heavy damage to another carrier for the loss of the
Lexington
and the crippling of the
Yorktown.
American fliers also downed a large number of enemy planes. Technically, in terms of ships sunk, it was a Japanese victory. But without carriers to provide air cover for the Port Moresby invaders, Yamamoto on May 18 called his ships and his occupation force back to Rabaul. Round one clearly went to the Allies.

Of larger significance, the Japanese for the first time in the war had suffered a setback. That realization gave the Allies' esprit a powerful boost.

 

 

Midway: "A Victory of Intelligence"

 

While Rochefort and his team were busy tracking the enemy's advance toward Australia from decrypted fragments, he also began detecting Ya-mamoto's Midway-Aleutians operation. Of special help was a decrypt of April 29 referring to the dispatch of maps of the Aleutian Islands. Another signal dealing with the "forthcoming campaign" used the words
koryaku butai
—"invasion force"—aimed at a destination encoded as
AF.
Rochefort and Layton informed Nimitz that something big was heading toward Hawaii.

In hindsight, it can be seen that Yamamoto's plans were flawed in the extreme. In setting the three objectives of taking the atoll, establishing control in the Aleutians and luring what was left of the U.S. Pacific Fleet out into the open sea, he was violating the principle of massing his strength. He thought of the Aleutian campaign as a useful feint, a clever deception, as well as a needed blunting of that northern scimitar hanging over the Japanese mainland. Instead it resulted in a ruinous division of his ships and carriers.

Cockiness made him sloppy. He allowed two other carriers to be left behind in home waters—one to be repaired after the Coral Sea battles, the other merely to receive a new complement of planes and pilots—when a determined effort could have added both to his fleet. In addition, when his huge force sailed toward Midway, he placed his four carriers forward in a close grouping that proved terribly convenient for U.S. attack planes. And instead of covering these all-important carriers with his battleships, he had the war vessels, including his flagship,
Yamato,
lag far behind, a floating headquarters remote from the action.

Most damaging of all was his attempt to use the same deceptive tactics at Midway that had worked for him at Pearl Harbor. Again he used fake radio traffic to create the illusion that his ships were in training operations near Japan. This time, thanks to the delay in introducing the new JN-25 code, Rochefort and his team were not to be fooled.

The intelligence supplied in the Coral Sea battles had confirmed for Nimitz that he could trust his codebreakers. When they began submitting evidence of a massive new Japanese thrust aimed at Midway, he sided with them against the view held by Washington analysts, as well as Washington chief Admiral Ernest J. King, that Rochefort was being duped. The Washington unit believed any move toward Midway was only a feint masking Yamamoto's real objective: the aircraft factories of Southern California. The U.S. Navy even dispatched a fleet, Admiral Morison has reminded us, to search for a Japanese carrier falsely reported to be descending on San Francisco.

Further, the Washington intelligence staff advised King that Halsey and his carriers should be kept in the Coral Sea, since the Yamamoto offensive might be directed there rather than toward Midway.

Rochefort was not subtle in disparaging these interpretations. Regarding an attack on the U.S. West Coast, he knew the Japanese lacked sufficient transports, tankers and food refrigeration ships to take on so remote an objective. Also, he judged it "ridiculous" and "stupid" to think they would strike so far east while the U.S. Navy ships at Pearl remained on their flank.

As for leaving carriers in the Coral Sea, MacArthur's codebreaking teams in Melbourne came to Rochefort's support. Their decrypts verified that the Japanese had abandoned amphibious operations against Port Moresby and were planning an overland offensive instead. Halsey's carriers could head for Pearl Harbor and Midway.

In his recorded oral reminiscences, Rochefort stated, "Possibly the best thing that ever happened to the Navy during the war was Nimitz's acceptance of Station Hypo's estimate of what the Japanese were going to do, not only at Coral Sea but at Midway and subsequent."

Even with Nimitz's approval, though, one big question remained. Where was
"AF"?
Rochefort had worked with the Imperial Navy's geographical bi-letter designations enough to know that
AH
was Hawaii and
AK
was Pearl Harbor. He was sure that references to
AF
in the intercepts stood for Midway, but none of the decodes made the identification certain. How could he make sure?

Lieutenant Commander Jasper Holmes knew that the Midway command depended on a plant that distilled seawater to supply the garrison's water needs. What if Midway sent out, both in plaintext and in a low-level code the Japanese were sure to read, that the desalinization plant had broken down and the island's supply of water was running desperately short? If
AF
was Midway, surely some mention of this crisis would show up in subsequent traffic.

The scheme was carried out, with the extra fillip of an answering plaintext transmission from Hawaii that a freshwater barge would be sent at once.

The deception worked. As Holmes reported, "The Japanese took the bait like hungry barracudas."
AF's
water troubles turned up in a decrypt, establishing beyond doubt that Midway was the target. Historian David M. Kennedy has called this resourceful stroke by Rochefort's team "the single most valuable intelligence contribution of the entire Pacific war." Its upstaging of the bigwigs in Washington, however, exacerbated their ill feelings toward Rochefort.

The ruse convinced Nimitz, who had already reinforced the defenses at Midway. He began preparing his David role against the Yamamoto Goliath, pitting twenty-seven surface warships against the enemy's eighty-eight. On May 25, Nimitz held a staff meeting that Rochefort had been ordered to attend. A punctual man, the admiral was annoyed when his chief cryptana-lyst showed up a half hour late. But when Nimitz saw what Rochefort had brought with him, all was quickly forgiven. Rochefort and his colleagues had spent the night decoding a long intercept. It revealed nothing less than the complete Japanese order of battle for the Midway attack. Plus, the intercept confirmed that the attack was scheduled not for mid-June, as Washington was claiming, but for June 3 or 4.

On May 28, the Japanese did switch to a new version of their JN-25 code, blacking out the Allied codebreakers for a time. But the changeover came too late. The Americans knew all they needed in order to take on the Japanese fleet.

Unlike the overconfident Yamamoto, Nimitz hastened to amass every element of naval strength he could muster. Although not an aviator himself, he understood the importance of naval air power. On the afternoon of May 27, the battered carrier
Yorktown
limped from the Coral Sea into Pearl Harbor. If it could be patched up in time, it would add a third carrier to Nimitz's fleet. Given the extent of its damage, the repairs could easily have consumed a couple of months, perhaps even a trip to the West Coast. Instead, crews swarmed over the vessel and on the morning of May 29 had it ready to put to sea, at least marginally battle worthy.

Nimitz received what seemed a serious setback to his plans when Bull Halsey arrived at Pearl with a skin disease that sent him to the hospital instead of aboard a flagship. Postmortems of the battle, though, suggest that in reality this was a felicitous change. The impulsive Halsey might not have fared as well in the complex operation as his cool, clear-thinking replacement.

This was Rear Admiral Raymond A. Spruance, who in his service under Halsey had shown himself to be an aggressive fighting man and a shrewd strategist. He would command one of Nimitz's task forces, with Jack Fletcher in charge of the other. Knowing from the Hypo codebreakers that the Aleutian operation was only a diversion, Nimitz sent northward a motley assortment of ships under Rear Admiral Robert A. Theobald.

On June 1, Yamamoto planned to place two picket lines of submarines between Pearl Harbor and Midway. The subs would be stationed there primarily to alert him if the U.S. fleet emerged in response to his surprise attack on the atoll. The operation was badly coordinated, and the subs were late in getting into position, but even if they had been on time they would not have detected the American ships; they had already passed the barrier.

For the previous month the defenses of the Midway atoll had been reinforced by inflows of antiboat and antiaircraft guns, two additional companies of GIs, five tanks, ten torpedo boats, stores of aircraft gasoline and a variety of planes that included B-17 Flying Fortresses. Midway was as ready as Nimitz could make it.