14

 

Up the Island Ladder Toward Tokyo

 

 

Japanese intelligence about Allied plans never played a serious role in the Pacific war. For the Allies the main intelligence problems came when their codebreakers were blacked out by the system changes the Japanese introduced as security measures. Then Allied commanders were prone to the same fumbling and bungling that characterized many of the Japanese operations.

Perhaps because of that unprincipled press release that broadcast the role of codebreaking in the defeat of the Imperial forces at Midway, the Japanese became rigorous in revising their code systems during the summer and autumn of 1942. The May 28 change from JN-25b to JN-25c plunged Allied crypto teams into almost total eclipse. As the summer progressed, troublesome changes were also made in the Imperial Navy's call sign systems. In August, just as Allied analysts were making some headway with JN-25c, the Japanese made another fundamental switch, from JN-25c to JN-25d. As Nimitz's staff report on August 1 noted dolefully, "We are no longer reading the enemy mail, and today we must depend almost entirely on traffic analysis to deduce enemy deployment."

Allied codebreakers struggled mightily to regain their mastery. A few useful decrypts resulted from an occasional Japanese regression to superseded codes. Otherwise, intelligence was reduced to the less exact arts of direction finding, traffic analysis and photoreconnaissance. Invaluable aid also came from the network of coast watchers, brave men the Australians put in place to transmit observations from within the Japanese perimeter.

This extended period of frustration for the cryptanalysts came at the time when the Japanese made landings in the Solomon Islands in late June and early August, and began constructing an airfield on Guadalcanal. Word of the development came primarily from the coast watchers.

Allied commanders knew they could not allow this venture to succeed. Guadalcanal would give the Japanese a new operational center 560 miles east of their major base at Rabaul in New Britain. From the new field, the emperor's bombers and Zero fighters could provide air support for landings on still more easterly islands. To prevent the Japanese from severing the lifeline between the U.S. and Australia, Guadalcanal must be retaken before the airstrip was completed.

In long, rancorous meetings in Washington, the U.S. high command had already decided on how the war in the Pacific should be conducted. The question was how to divide responsibilities between the two strong leaders Nimitz and MacArthur. Nimitz believed that the best route to Tokyo lay along the small islands in the mid-Pacific. MacArthur, obsessed with his pledge to return to the Philippines, favored a great arc north out of Australia and northwest along the big islands of New Guinea and New Britain, concentrating on seizing Rabaul. The Joint Chiefs of Staff had compromised by endorsing both plans and drawing a line of demarcation with MacArthur in charge to the west and Nimitz commanding operations to the east. Guadalcanal lay just barely within Nimitz's vast area of control.

Being surprised had become almost standard operating procedure for the clueless Japanese military. So it was with Nimitz's August 7 landing on Guadalcanal. The small Japanese contingent on the island, mostly laborers, offered little opposition to the invaders. In just thirty-six hours the Marines had captured the airstrip, which they named Henderson Field in honor of a flight commander who had died leading an attack at Midway. Tulagi, the island adjacent to Guadalcanal, was seized after suicidal resistance by the Japanese troops occupying it.

American commanders, having to proceed without guidance from their codebreakers, were also vulnerable to surprise. That came on the night of August 8, when a Japanese fleet slipped past Savo Island off Guadalcanal and attacked the warships protecting the landing. Four heavy cruisers—three American and one Australian—were lost to the Japanese guns and highly superior Long Lance torpedoes. The ships supplying the Marines ashore backed off after delivering only half their supplies and food. When the engineering equipment needed for work on the airfield was withdrawn, the Marines used abandoned Japanese machines to do the job.

In a tragic twist, Allied intercept operators had delivered into cryptanalysts' hands the message detailing the Imperial Navy's planned course of action off Guadalcanal, but the codebreakers were unable to solve it until two weeks after the battle had been fought.

The Battle of Savo Island was the first of seven naval engagements that battered both antagonists over the next six months. Each side had twenty-five ships sunk—so many that the waters there came to be known as "Iron-bottom Sound." As noted by Guadalcanal veteran Phil Jacobsen on his Web history of the Pacific war, the total of Allied sailors who lost their lives at sea was more than three times that of Marines and GIs killed on land.

Meanwhile, the struggle on Guadalcanal surged back and forth in the island's fetid jungles and malarial swamps. The Japanese, recognizing that the loss of the island would punch a dangerous hole in their defense perimeter, were as determined to retain the island as the Americans were to drive them out.

Japanese movements were being tracked by an unseen foe. Even when Hypo and Melbourne were blacked out, the coast watchers filled in. On September 30, 1942, for example, they warned of a cruiser force heading toward Guadalcanal to bombard the Marines there and put Henderson Field out of commission. So warned, an American fleet met them in the Battle of Cape Esperance. It was a confused struggle, a strategic draw in terms of damage done, but the Japanese ships turned back.

The time of drought for the main Allied cryptographic centers finally ended. In late August they began breaking into the new JN-25 code and by late September were reading it expeditiously enough to supply useful tactical information. When on October 1 the Japanese activated a new substitution table meant to throw off cryptanalysts, the Allies broke it in two days.

With Henderson Field planes controlling the air by day and Allied intelligence units guiding the destruction of large-scale attempts to reinforce and supply Imperial troops on Guadalcanal, the Japanese were reduced to night runs, which became known as the Tokyo Express. Even a number of these runs, however, were anticipated and the transports sunk.

Frustrated, the Japanese high command decided in November to mount one more strong effort to dislodge the Marines. The Tokyo Express landed so many reinforcements that for the first time, the Japanese outnumbered the Americans on the island. Admiral Yamamoto, revered despite the Midway disaster, commanded a task force that sought to add to those gains by bombarding Henderson Field while eleven transports ferried in additional infantrymen and tons of supplies.

The codebreakers told Bull Halsey, now in overall charge of the American and Australian fleet, what to expect. There followed three days of vicious righting, the two naval battles of Guadalcanal. Poorly commanded American ships suffered severe losses, but the Japanese fared even worse. Most important, eight of the Japanese transports were sunk and thousands of the soldiers drowned.

By the first week of December, the Tokyo Express was limited to runs by submarines bringing in wholly inadequate supplies to the sick and starving troops. Allied decrypts foretold another desperation measure: a run by fast destroyers bearing 1,200 drums of supplies. Halsey saw to it that the destroyers were shot up and turned back. Only 220 of the drums reached land.

The time for the denouement on Guadalcanal had arrived. In late January 1943, decrypts alerted the Allies to a Japanese plan for a new series of warship runs to the island. What the messages failed to disclose was that the ships were not there to bring in reinforcements. Their purpose was evacuation. The Tokyo Express rescued thirteen thousand emaciated soldiers, all that were left of the thirty-six thousand who had come there to fight. By contrast, American losses were just over a thousand dead.

Nimitz sent out a message that read, "Once again radio intelligence has enabled the fighting forces of the Pacific and the Southwest Pacific to know where and when to hit the enemy." He added, "My only regret is that our appreciation, which is unlimited, can be extended only to those who read this system."

Bull Halsey liked to think of the islands of the Pacific as a ladder, with each newly won island a rung in the climb toward Tokyo. Guadalcanal, now finally and irrevocably in Allied hands, was the first rung of the ladder to be ascended.

 

 

Hitting the Japanese Where They Weren't

 

In the division of Pacific war responsibilities dictated by the Joint Chiefs, Nimitz was required to provide MacArthur with naval support. In another of his smart decisions, Nimitz sent Halsey to work with The General. The two of them hit it off swimmingly, forming an ardent mutual admiration duo. In his MacArthur biography, American Caesar, William Manchester has told how MacArthur, after his first meeting with Halsey, clapped the admiral on the back and said, "If you come with me, I'll make you a greater man than Nelson ever dreamed of being."

Together they put into practice the strategy of finding out from intelligence where the Japanese were most expecting an attack and then striking their weaker spots somewhere else. For example, Halsey found out that the Japanese, after losing Guadalcanal, anticipated that the next target in the Solomons would be the island of Kolombangara, and they armed the island with ten thousand troops. Instead, Halsey bounded past them and seized Vella Lavella, garrisoned by fewer than a thousand. Outflanked, the Japanese had to evacuate Kolombangara, giving it up with scarcely a shot being fired. Similarly, on the large island of Bougainville, Halsey leapfrogged past the most strongly fortified base, at Buin, and sent his troops ashore at Empress Augusta Bay, farther along the coast. So he and Nimitz began climbing the island ladder.

MacArthur planned similar tactics on New Guinea. His first try, however, did not work out as he had hoped. When the Japanese had been stopped short of Port Moresby and their disease-ridden remaining troops were ordered to withdraw back over the Owen Stanleys, he directed that a pincer attack be made at Buna, on New Guinea's northern coast. His idea was to have a newly arrived American infantry division press from the land while an amphibious force came in from the sea. The General expected a quick victory over a weak garrison. The importance he attached to the Buna offensive is indicated by his final words to his field commander, General Robert L. Eichelberger: "Bob, take Buna or don't come back alive."

His twin attacks did surprise the Japanese, but then MacArthur encountered his own surprise. Instead of facing a few jungle-weakened, battle-weary survivors, his troops faced a large cadre of fresh reinforcements. The battle for Buna turned into a protracted, costly campaign.

Buna taught MacArthur several lessons. One was that he could not afford never going to the battle sites himself. By staying back at his spacious, elegant quarters at Port Moresby and letting his field commanders direct the fighting at Buna, he strengthened his GIs' estimation, and for many their detestation, of him as "Dugout Doug." Second, he learned not to allow his field officers to send their troops in direct frontal assaults if any other course was possible. On Buna these tactics cost almost twice as many men as were lost on Guadalcanal. And he might well have learned not to deepen the common soldiers' antipathy by issuing more of his grandiloquent communiqués, one of which at Buna claimed, in the face of what every GI knew to be false, that "probably no campaign in history against a thoroughly prepared and trained army produced such complete and decisive results with so little an expenditure of life and resources." This last lesson, though, was probably more than his imperial character could absorb.

Although Buna was a low point for him, the ultimate defeat of the Japanese there did force them finally to abandon any lingering hope of taking Port Moresby. It gave MacArthur a foothold to begin his daring moves up New Guinea's northern coast. And yes, Eichelberger did come back alive.

After Buna, The General corrected his image by becoming almost too visible to his combat troops. When his paratroopers were making their first landing on the New Guinea coast, he insisted on going along in the lead plane. When his troops made beach landings, he arrived while the fighting was still intense, striding forward helmetless, in his pushed-up gold-braided cap and noncamouflaged khakis, smoking his corncob pipe, and persisted in walking so near the front lines that he could poke with his toe at the still-warm bodies of snipers shot out of the trees. When others in his entourage dived for cover, he remained upright, presenting a target that, miraculously, never got hit.

In March 1943, Allied codebreakers set up another victory. A decrypt warned that the Japanese, determined not to give up another inch of the New Guinea coast, were dispatching to their base at Lae an infantry division of seven thousand troops, transferred from Korea and north China. The soldiers were to be conveyed from Rabaul in eight transports, escorted by eight destroyers.

Major General George C. Kenney, MacArthur's air chief, had already been working closely with the codebreakers in planning his air strikes. He read their decodes about the convoy as a fine opportunity to test out new antiship tactics he'd instituted. Bombs dropped from a great height, he had decided, rarely hit their targets. His alternative was to train his medium-range bomber crews to swoop in at a low level and send their fragmentation bombs skipping over the water like flat stones thrown from the beach. The bombs were timed to detonate only after they had penetrated the ships' hulls.

His skip-bombing techniques won the day in the Battle of the Bismarck Sea. Told by the cryptanalysts where to look, Kenney's recon planes spotted the convoy. Its ships were first intercepted by Flying Fortresses employing their precision bombing from on high. They sank only one ship. The next day, when the Japanese Zeros were high up in anticipation of another Fortress raid, Kenney's skip bombers sneaked in just above the wave tops—a neat turnaround on the tactics that had won at Midway. All eight of the transports, as well as four of the destroyers, were sunk, with the loss of thousands of Japanese troops. The battle put an end to Japanese attempts to move anything larger than a small barge by daylight when they were within range of Allied aircraft.

In the months that followed, MacArthur made slow, slogging progress up New Guinea's northern coast. By late January 1944, he had still gone only about a third of the way and faced strengthened Japanese defenses along the island's western two-thirds. However, another important cryptologic change had taken place. Previously MacArthur had been largely dependent on decrypts of Japanese naval codes; the army codes resisted penetration. But as the Allied troops pushed back the Japanese in the battles at a place called Sio, an engineer with a mine detector discovered a bonanza. The retreating infantry had buried a steel trunk that contained the division's entire cipher library. Within days Central Bureau was decoding army messages by the thousands.

The army and navy decrypts combined to tell MacArthur that the Japanese were expecting his next amphibious attack to be launched against Wewak and Hansa Bay, not far from his previous advance. They were so sure of what he would do that they had begun reinforcing their defenders at these sites, including shifting troops from their base much farther along, at Hollandia (now called Jayapura). On the strength of this information, The General decided not to take the small, expected step. He would make the big leap to Hollandia.

Most commanders regard military strategy from within the confines of their own particular service. Army officers, for example, are apt to regard water as a hostile environment. Not MacArthur. He, with Halsey in charge of his naval wing and Kenney the air, became adept at what the admiring Churchill called "triphibious" operations. According to Manchester's biography, during the Pacific war MacArthur made eighty-seven end-around thrusts from the water, and all of them were successful.

None was more so than his triphibious operations at Hollandia. Nimitz contributed by supplying carrier-based air support, but, concerned about exposing his carriers to Japanese bombers, he limited their participation to just three days. MacArthur responded by planning an additional landing at Aitape, 125 miles southeast of Hollandia. Capture of the Japanese airfield there would assure him of continuing air cover. His staff also worked out an elaborate series of deceptions. Kenney's planes played to Japanese preconceptions by bombing and strafing Hansa Bay defenses and by conducting highly conspicuous reconnaissance flights. Torpedo boats made themselves obvious in the area. Submarines left empty rafts ashore to suggest that patrols had been there to investigate landing sites. And when the Allied flotilla sailed toward Hollandia, the ships made feints toward the Wewak and Hansa Bay strongpoints, then at night swerved toward their real target.

MacArthur's quantum leap went off with few hitches. The landings at both Aitape and Hollandia were unopposed. Troops of the small Japanese garrisons faded into the jungle, most of them dying of starvation or succumbing to disease while trying to reach the nearest friendly base. The airfields were captured, and Nimitz's carriers retired without loss. A strong Allied force held the ground separating Japanese strength to the west from that to the east.

Edward Drea's MacArthur's Ultra summed up the Hollandia offensive as the codebreakers' "single greatest contribution to The General's Pacific strategy." Drea also saw it as a masterpiece of integrating signals intelligence "into operational planning to deceive, outmaneuver, and isolate an opponent."

By this one daring leapfrog of an attack, MacArthur had extended his control to halfway along New Guinea's fifteen-hundred-mile northern coast—and a lot farther toward his goal of stepping again on Philippine soil.

Perhaps the most telling commentary on MacArthur's tactics was that given after the war by Japanese intelligence officer Colonel Matsuichi Juro. He called The General's envelopment techniques "the type of strategy we hated most." Juro described how, repeatedly, MacArthur, "with minimal losses, attacked a relatively weak area, constructed airfields and then proceeded to cut the supply lines. . . . Our strong points were gradually starved out. . . . The Americans flowed into our weaker points and submerged us, just as water seeks the weakest entry to sink the ship. We respected this type of strategy . . . because it gained the most while losing the least."

While these land and air battles were proceeding satisfactorily, the Allied and Imperial navies were battering each other in a series of engagements. Although in these battles the Japanese generally sank more ships than they lost, the factor of fleet attrition was coming to the fore. The fighting in the South Pacific claimed far more warships, especially destroyers, than Japan's production could replace, while American shipyards were sending veritable armadas of new vessels down the ways. Also, Yamamoto had expended much of the cream of Japan's experienced fliers in ill-advised attacks, many of which were tipped off by Allied codebreakers, against strongly fortified targets. Well-trained airmen were another resource Japan was not replenishing.

It was in these waters that John F. Kennedy, skippering patrol torpedo boat PT-109, had his close call with early death. Patrolling off the Solomons on August 2, 1943, Kennedy had his boat rammed, split in half and set afire by a Japanese destroyer. Two of the crew of thirteen were killed outright and a third was badly burned. Towing the injured man by clenching the ties of his life jacket in his teeth, Kennedy led the others on a four-hour swim to Plum Pudding Island, well within the Japanese area of control. Fortunately the destruction of PT-109 had been sighted by a coast watcher. After six days of hiding out and of desperate recon swims by Kennedy, who had been on the Harvard swim team, the eleven survivors were found by natives who were pro-Allies, and a rendezvous was arranged with another torpedo boat. Kennedy's life was spared probably by the impotence of Japanese cryptanalysts. The codes used by the coast watcher in reporting the loss of his boat and arranging his crew's rescue were ones that even a moderately skilled analyst should have solved. But only Allied receivers read the messages, and the rescue operation went off without interference.

 

 

Codebreakers Plot Yamamoto's Fall

 

One of the most thankless but necessary tasks of intelligence units was the deflation of exaggerated battle reports. Allied codebreakers could set the records straight, but Admiral Yamamoto had no comparable service to correct his fliers' overoptimism. His spirit was buoyed, therefore, by the inflated claims of success by his aviators in their series of raids meant to blunt any planned offensive the Allies might try after Guadalcanal. The admiral came south to Rabaul to begin a tour in which he would review operations and encourage his men. Allied cryptanalysts intercepted messages that offered a tempting possibility: Yamamoto's itinerary would bring him within range of planes lifting off from Henderson Field. Since Yamamoto was known to pride himself on his punctuality, he and his retinue could be expected to follow a precise schedule. Did the Americans dare an aerial ambush?

It was a vexing question. Japanese confidence in their code systems still held. But if American planes suddenly appeared in the correct time and place to intercept Yamamoto's tour—wouldn't that convince the most diehard believer that the Japanese system had been compromised?

When Admiral Nimitz was presented with the decrypts, his answer was to go for it. The removal of so venerated a leader would count for far more than the possible jeopardy to this one phase of Allied codebreaking. Besides, the coast watchers provided a viable cover story: personnel involved in the mission, and thus vulnerable to capture, would be told that the information came from informants at Rabaul. Nimitz secured the approval of the higher-ups in Washington.

On the morning of April 18, 1943, a flight of sixteen fighters took off from Henderson Field and flew at wave-top height to sneak under radar detection and avoid sightings by pro-Japanese coastal watchers. The American timing had to be precise. Even with drop tanks, the four-hundred-mile distance to the point of interception was at the far edge of the P-38s' limits; they couldn't wait around for Yamamoto and his escorts to appear.

There was no need to worry. The two Mitsubishi bombers bearing the admiral and members of his staff, along with protecting Zeros, were right on time. Part of the American flight soared up to take on the Zeros and provide cover. The other planes slipped in, raked the bombers with fire and sent the one bearing Yamamoto flaming into the jungle.

The admiral's death had the desired effect. When it was belatedly reported to the public in May, the Japanese people were profoundly shocked. Many later traced their disheartenment with the war to that moment. Yamamoto, always a dangerous offensive force, was replaced by a conservative, defense-minded strategist.

As David Kahn summed up the episode, "Cryptanalysis had given America the equivalent of a major victory."

 

 

Nimitz Goes Island-Hopping

 

While MacArthur was making end runs up the long coast of New Guinea, Chester Nimitz was intent on forcing the Japanese to contract the perimeter of their Greater East Asia Coprosperity Sphere.

He was having to plan without the services of Joe Rochefort. In the autumn of 1942 the credit war claimed Rochefort as victim. His superiors in Washington, regarding him as a prickly obstacle in the way of their earning plaudits for major intelligence coups, continued to be incensed that he had made fools of them in their off-the-mark predictions. In October he received orders to report for temporary duty at the Office of Naval Operations in Washington. His staff thought this would be good for him. He would gain a respite from the hard work and bad air-conditioning at Pearl Harbor that had given him a persistent bronchial cough and caused him to lose a lot of weight. He might, in transit, get to spend a few days with his family in California. He might even be given a decoration or promotion.

Rochefort knew better. Benefits were not what Washington had in mind. By then Naval Intelligence had been taken over by Admiral Joseph R. Redman, who had eased out Laurance Safford, OP-20-G chief and a good friend of Rochefort. In Safford's place, Redman had installed his younger brother, John. For Admiral Redman, a primary personal objective was to gain control over the intelligence network of the U.S. Navy. As Rochefort said in his reminiscences, Redman wanted "to have somebody on Hypo that would be a creature of his, and this obviously was not going to be Rochefort." Turning over to Jasper Holmes a package of personal papers and the keys to his desk, Rochefort predicted to his doubting colleagues that he would not return to Pearl Harbor.

His assertion was quickly verified when he reached Washington. He was accused of "squabbling" with Nimitz's staff members, opposing a recent reorganization and failing to keep his headquarters informed. After a brief stay in Washington, he was eventually assigned to the Tiburon peninsula in California, where he served as an instructor in the Floating Drydock Training Center. With Rochefort out of the way, the Redman brothers wrote their own history that claimed Midway as an OP-20-G triumph and gave Rochefort only the briefest, most grudging mention.

So mean-spirited were they that when Nimitz recommended Rochefort to receive the Distinguished Service Medal, they saw to it that the award was blocked. In 1958, when Nimitz tried again, he was told that the time had passed for awarding medals in recognition of World War II service. It was not true: Rochefort was granted the medal. The only trouble was that by that time he had been dead for nine years.

The Navy's chief of staff, Admiral Ernest J. King, did salvage some of Rochefort's intelligence skills and knowledge. In late 1944 he recalled Rochefort to join a special group preparing intelligence summaries for him. But Rochefort's time in the Floating Drydock Training Center was a long year lost to Allied intelligence—and what a mockery of an assignment it was for the man responsible, in the words of his associate Holmes, for "the greatest intelligence achievement in the Navy's history."

Meanwhile, late in March 1943, Hypo's codebreakers warned Nimitz that a Japanese convoy was being sent to reinforce the troops holding the Aleutian islands of Attu and Kiska. Nimitz organized a task force to intercept. In an inconclusive sea battle, the Americans succeeded in turning back the reinforcements only because the Japanese vice admiral, at the critical moment when his way was actually clear to make the landings, chickened out and withdrew—and was summarily relieved of his command.

During May, Nimitz assigned an infantry division to retake Attu. The conquest cost the Americans more than five hundred lives, but of the Japanese garrison of twenty-five hundred men only twenty-eight survived after one last banzai sake-soaked suicidal charge. When the U.S. troops moved on to attack Kiska, they found that under the cover of an impenetrable Aleutian fog the Japanese had evacuated their entire force. The northern arc of Japan's defense ring no longer extended to American shores.

In Nimitz's island-hopping campaign across the central Pacific, his targets were much different from MacArthur's. The General most often plotted his course over large land masses—New Guinea is approximately the same in land area as Alaska. The great coastal distances gave him opportunities for his clever triphibious operations. Nimitz, on the contrary, faced clusters of tiny atolls, mere pinpricks of land in the vast reaches of the Pacific. His formula for success had to be quite different: send in ships and planes to bombard the immediate island as near to rubble as possible; then dispatch troops in landing craft headed for the beaches and cover their approach with air, bombardment and naval gunnery. MacArthur complained to the chiefs of staff about the enormous losses of lives resulting from Nimitz's tactics, but one wonders whether he could have managed a real alternative or was just undercutting a rival commander. This much is true: when The General did have to take a small island, such as Biak, off the northwestern end of New Guinea, he used a frontal attack, ran into fanatical dug-in Japanese resistance and suffered a considerable number of casualties.

On November 20, 1943, Nimitz launched the first of nine atoll landings he would make in his approach to the Philippines. His objective: atolls in the Gilbert Islands, most particularly Makin and Tarawa. These bits of sand and coral, on the outer edges of Japan's defense perimeter, Nimitz regarded as threats that must be eliminated before he moved on to more important seizures in the Marshall Islands.

The Americans faced unprecedented challenges in conducting this kind of atoll warfare, and their first try was a disaster. Even though signals intelligence identified the Japanese units and determined their numbers almost to a man, the Sigint advantage could not offset the botched execution of the invasions. The opening aerial and naval bombardments, which seemed annihilating to the officers involved, actually did little to weaken the defenders, holed up in caves and tunnels or protected by parapets of concrete and palm logs. The bombardments were not well coordinated, leaving lapses that allowed the Japanese soldiers to recover and reestablish themselves. Confusions and snafus in the landing operations exposed men needlessly to Japanese fire.

Makin, now named Butaritari, was known to be only lightly garrisoned and was expected to fall in hours. Instead, its die-rather-than-surrender Japanese held out so stubbornly that only in the third day could the U.S. field commander radio, "Makin taken." The delay gave a Japanese submarine time to sneak in and sink, with heavy loss of life, an aircraft escort carrier that would long since have withdrawn if the battle ashore had gone more swiftly.

The horrors of Tarawa shocked the nation. U.S. Marines descended on the main island of Tarawa's ring of atolls expecting to find the enemy dead or dazed by the fierce prelanding bombardment. Instead they encountered Japanese gunners zeroed in to blast many of the landing craft out of the water. Because of bad forecasts, the invasion fleet headed for the beaches at the time of an exceptionally low tide, with the result that the landing craft hung up on hidden reefs. The Marines had to wade in thigh-deep water for more than a hundred yards under devastating fire. The remnants of the main force who made it ashore had to fight for the island inch by inch, using hand grenades and flamethrowers to subdue the defenders. The battle went on for a murderous seventy-six hours. Photos of dead Marines sinking facedown in Tarawa sand brought to the American public a fresh awareness of what victory in the Pacific war would entail.

Tarawa was a hard learning experience. By the time Nimitz was ready to invade the Marshalls, he made sure more accurate data foretold water levels and tide changes. Teams of frogmen went in with demolition charges to clear away barriers. Improved landing craft were designed and rushed to the Pacific. Scores of other improvements included more destructive bombardment patterns, better disembarkation procedures, stronger ground-to-air radio liaison and new methods to subdue Japanese strongholds.

Nimitz, as ever, based his decisions for the Marshalls strike on what his codebreakers were telling him. Decrypts confirmed that the Japanese were expecting the attacks to fall on the outer rim of atolls and in this expectation were shifting troops out of centrally located Kwajalein to these peripheral outposts. Nimitz's decision to land on Kwajalein startled his staff as well as the Japanese.

Decrypts had also shown that the Marshalls' defenders lacked the aircraft to mount a full-scale surveillance of their perimeter and were consequently focusing their searches on the most likely approaches from the south and southeast. Nimitz directed his U.S. Navy task force to drive in from the unguarded northeast. As a result, conquest of Kwajalein and its neighboring atolls in early February 1944 went forward in an orderly fashion, with a third of the casualties suffered at Tarawa. The taking of Eniwetok, farther west in the Marshalls, was more savagely contested by another suicidal Japanese defense, but it, too, fell in five days and was secured by February 21.

Meanwhile, in the southwest Pacific, MacArthur had cleaned the Japanese out of New Guinea except for guerrillas hiding and starving in the hills and had seized the islands of Wakde and Biak, off the big island's northwest coast.

Originally the Nimitz-MacArthur pincer movement was meant to close in on the Japanese stronghold of Rabaul. Now they no longer saw the need to spend lives battling the hundred thousand Japanese troops stationed there. Rabaul could be reduced by bombing and naval firepower and left to wither on the vine. The more northerly fortress at Truk was similarly pounded into a smoking ruin and bypassed.

With all of this favorable news unfolding, MacArthur could look northward with lip-smacking anticipation: his next move would land him on Philippine soil.

 

 

Massacre of the Marus

 

Studying the reports on the war in the Pacific, one can't help but wonder how the Japanese failed to conclude that their codes were being broken. This wonderment pertains especially to the movements of Japanese transport vessels, the marus trying to shift troops or bring supplies to Japanese outposts and meet the import needs of the Japanese nation. Having broken JN-11, the "maru code," the codebreakers time and again foretold when Japanese ships were scheduled to leave port, the planned course of their voyages, their stops for refueling and their expected times of arrival at their destinations. And time after time the marus were intercepted by Allied ships, submarines or planes and destroyed. The decrypts became so numerous that the informants no longer concocted cover stories as to how else the information might have been obtained. They simply sent out a message and let the Allied attackers follow up on it, confident that the Japanese would never lose faith in the inviolability of their codes.

Allied submarines, in particular, showed up wherever Japanese ships went. The accepted explanation seemed to be that the Allies had so many subs they simply blanketed the Pacific with them. A Japanese prisoner reported that in Singapore it was a common saying that one could walk from that port to Japan on American periscopes. The reality was summed up in Jasper Holmes's memoir: "There were nights when nearly every American submarine on patrol in the Central Pacific was working on the basis of instructions derived from cryptanalysis."

Historian John Winton has determined from official sources that while submarines constituted only two percent of the American war effort in the Pacific, they sank two-thirds of the total merchant-ship tonnage and one out of every three Japanese warships sent to the bottom.

American subs achieved these results despite having to rely on torpedoes that, for nearly the first two years after Pearl Harbor, often proved defective. They had two main flaws: their guidance systems frequently caused them to go too deep and pass under their targets, and even when they hit, their faulty detonators failed to make them explode. Submarine captains often heard their torpedoes thump against the sides of the enemy vessels without going off. Ordnance officials continued to claim that the trouble lay with the captains: they were incompetent; they couldn't aim properly. But the contrary evidence mounted, bolstered by codebreakers' receipts of Japanese messages reporting such incidents as ships arriving in harbor with unexploded torpedoes embedded in their flanks. New designs finally corrected the flaws, and the submariners' scores improved.

The Japanese were indefatigable reporters. They not only supplied the Allies with full information about their shipping schedules; they also aired their losses. The codebreakers were, consequently, able to confirm the results of Allied raids.

In the last months of 1943 and throughout 1944 the sinkings reached incredible rates. In November 1943, a total of 120 decrypts were transmitted to the submarines, with another 40 messages adding to or correcting the originals. These guided the subs in sinking 43 ships, of 285,820 tons, and damaging another 22 vessels, of 143,323 tons, making a total of 429,143 tons in one 30-day period. In December a U.S. sub scored the first Allied sinking of an aircraft carrier.

During 1944 the sinkings reached their peak. No less than 548 vessels totaling 2,451,914 tons, went down. So many tankers were sunk that fuel became a desperate problem. The subs sank a converted ferry, gunboats, a cruiser. Trying to reinforce threatened island garrisons by transferring troops from Taiwan and Manchuria, the Japanese had many transports sunk, with heavy losses of soldiers adding to those of the sailors.

While at the outset of the war the submarine strength of the Imperial Navy roughly equaled that of the U.S. Navy in the Pacific, the Japanese made ineffectual use of their subs. One important reason was that their submarine crews disdained attacking merchant vessels; they were at war to take on warships. The result was that they never tried to cut off the supply lines from the U.S. to Australia. As the war proceeded, the Japanese began more and more to use their subs in all sorts of tasks, such as carrying supplies, that might better have been left to other types of vessels. The subs became so ineffective a threat to Allied shipping that the U.S. soon stopped bothering with convoys and began sending out transports unescorted.

As 1945 began, the rate of sinking by Allied submarines declined, for one significant reason: they simply ran out of targets. Their stranglehold on the Imperial war machine and the Japanese economy was all but complete.

The postwar tribute penned by U.S. Vice Admiral Charles Lockwood included a compliment that, though a bit backhanded, says it all: "During periods, which fortunately were brief, when enemy code changes temporarily cut off the supply of Communication Intelligence, its absence was keenly felt. The curve of enemy contacts and of consequent sinkings almost exactly paralleled the curve of Communication Intelligence available."