CHAPTER 28

“THE WAR GAMES”

At about 0900 on September 11 limousines and other vehicles piled up in front of the huge iron-gated entrance of the Imperial Naval Staff College.1 Seasoned admirals and aspiring staff officers alike looked forward eagerly to this yearly visit to Tokyo. Everyone enjoyed renewing old friendships, and “there was always a certain amount of drinking and hell raising. . . . ”2 To these important exercises came most of the sharpest minds and the best staff officers of the entire Japanese Navy. A few Army officers also attended in a liaison capacity.

In the east wing, which housed Yamamoto and his Combined Fleet officers, was a secluded room, strictly off limits to all but those expressly invited to enter. We shall call this the Secret Room; here the First Air Fleet rehearsed the plan to attack Pearl Harbor.

The first day of the war games broke in the participants gradually with a “preexercise discussion” lasting only from 0900 to 1300. The next day, Friday, September 12, work began in earnest with a full schedule from 0800 to 1700 and continued through Tuesday, the sixteenth.3 Yamamoto presided over the exercises conducted in accordance with the Combined Fleet’s war plan. In simulating combat conditions, he divided his warships into task forces allocated to the numerous operations. These groups in turn split into Blue Forces representing Japan and Red Forces simulating the Americans and British. The chief of staff of each fleet usually acted as its Blue commander. Ugaki headed all the Blue Forces, while Vice Admiral Shiro Takasu, Commander in Chief of the First Fleet, ran the Red Forces.

The Blue team would carry out as faithfully as possible the operations which the Combined Fleet projected. Red Forces operated according to plans which their commanders submitted beforehand. As the games progressed, the umpires, of whom Ito was chief, determined changing operational conditions in cooperation with the Red Forces, to keep the exercises as realistic as possible and to hide Red plans from the Blue commanders. In many cases the officers chosen to represent Red had been picked because of their specialized knowledge of the countries involved.

The war games posed a massive problem: how to seize control of the Philippines, Malaya, and the Netherlands East Indies, cope with the enemy fleets stationed in those areas, and at the same time maintain control of the western Pacific. A unique feature of these games was the extension of Japan’s inner defense line far eastward from the Marianas, near which traditional strategy predicated the Great All-Out Battle, to the Marshalls.4 At the same time the Japanese had to prevent a damaging thrust into their exposed flank from American naval forces ranging out of Hawaii.

No one can understand the Pearl Harbor venture except in relation to Japan’s major war plans. Having deliberated the problem all year, Tomioka and his Operations Section officers determined that if and when Japan went to war, it should snatch the southern treasure chest quickly and efficiently.5 When he and his men took their places at the Naval Staff College, they already knew the roles which the various fleet units would play, having rehearsed these in table maneuvers in their Tokyo offices from September 3 to 5.

The war games followed much the same path as the actual Southern Operation was destined to take. Fleet commanders, size and composition of forces, points of departure, areas of rendezvous, strategic objectives, and landing beaches were virtually identical.6 Bent with absorbed attention over broad tabletops, the admirals of the Southern Command and members of the Naval General Staff watched Vice Admiral Ibo Takahashi’s Third Fleet simulate its assigned mission against the Philippines, Borneo, and Celebes.

While the Third Fleet made its move in the maneuvers, the Eleventh Air Fleet based on Formosa attacked MacArthur’s air forces at Clark and Nichols fields in a series of surprise bombing raids.7 In concert with Takahashi’s and Tsukahara’s operations, Vice Admiral Nobutake Kondo led his Second Fleet of battleships, cruisers, and destroyers out of Mako in the Pescadores, while from Hainan Island off the China coast sailed the Southern Expeditionary Fleet, a large, mixed flotilla under Vice Admiral Noboru Hirata. Swinging southward in a feint toward Bangkok, these two invasion units under Kondo’s command headed for Malaya in a three-pronged assault against Singora, Patani, and Kota Bharu more than halfway down the peninsula. From these strategic points Japanese troops would drive down the jungle-covered land toward Singapore, key to Britain’s, position in the Far East. With its fall the props would be knocked from under Britain’s Empire in Southeast Asia, the communications line to Australia severed, and the floodgates to the Netherlands East Indies flung wide.

As the Imperial Navy’s ships plowed in imagination through the South China Sea, Rear Admiral Sadaichi Matsunaga’s Twenty-second Air Flotilla, land-based in Indochina, prowled the skies in search of enemy ships and planes. Well-balanced invasion units also sortied from Camranh Bay in Indochina to land at Miri and Brunei Bay in British Borneo, more than 2,500 miles from Tokyo.

The Navy had not yet worked out detailed invasion plans for the Netherlands East Indies.8 Nevertheless, it had defined the broad outlines of strategy. The Japanese planned to slice through the Macassar Strait, seize Tarakan and Balikpapan in eastern Borneo, take key points on Celebes, conquer Bali, and then concentrate their strength for the final push against Java.

Other Japanese forces in this monumental game of naval chess sailed to the Gilberts, Guam, and Wake.9 Seizure of the latter two islands by Vice Admiral Shigeyoshi Inoue’s Fourth Fleet would bar the United States from Japanese waters and add several more unsinkable aircraft carriers to Japan’s island bases. Above all, it would put the Combined Fleet in an excellent position to fight the Great All-Out Battle if and when the United States Navy decided to gratify this desire on the part of the Japanese.

Onishi in particular stressed the necessity for more planes to carry out the Southern Operation successfully.10 The schedule for advancing air forces to the Java line lagged heavily in the case of Zeros and to a lesser degree in that of land-based planes. Therefore, most participants expressed their opinion that all of Japan’s carriers should be used in the Southern Operation, on which rested the rise or fall of the Japanese Empire.

Having seen the rehearsals for the Southern Operation well on the way to a logical conclusion, Yamamoto could devote his best energies to his Pearl Harbor scheme. He brought with him to the Secret Room Ugaki, Kuroshima, Watanabe, Sasaki, and Arima. The date was Tuesday, September 16.11

Some thirty-odd handpicked officers crowded toward the center of the room, intent upon a long table littered with papers. Maps of the Pacific hung from the walls, with Oahu and Pearl Harbor clearly marked as the targets. Standing over the table, Yamamoto dominated the proceedings. He had personally screened the officers to be admitted to the Secret Room, choosing only those who eventually had to pass on his Pearl Harbor project, help plan it, or execute it.12

Nagumo, still prey to deep misgivings, was present with most members of his First Air Fleet staff—Kusaka, Oishi, Genda, Yoshioka, and Sakagami. From the Second Carrier Division came its rambunctious Commander in Chief, Yamaguchi, with several of his staff, including Suzuki.

Here too in the Secret Room was a relative newcomer to the Hawaiian venture, Vice Admiral Gunichi Mikawa, who was to lead the Pearl Harbor Support Force, consisting of the Third Battleship Division and Eighth Cruiser Division. A man of medium height, as sturdy and strong as the capital ships he commanded, Mikawa bore his fifty-three years with easy grace. He believed in the concentration of forces; consequently, he thought that “the plan to carry out an attack against the U.S. Fleet and the Southern Operation at the same time” overloaded the capabilities of the Japanese Navy and jeopardized the success of both operations.13

Another newcomer, Rear Admiral Sentaro Omori, Commander in Chief of the First Destroyer Squadron, was present. He looked as subdued and appealingly shy as an elf escaped from Walt Disney’s drawing board. But he was all sailor. When he learned about Pearl Harbor, Omori’s biggest worry became “how to get his destroyers all the way to Oahu and back.” Both Mikawa and Omori insisted that they heard about Yamamoto’s plan for the first time at these war games.14

Present, too, were the key officers from the Sixth Fleet: Shimizu, handsome and dignified; his resourceful chief of staff, Mito; and his senior staff officer, Commander Midori Matsumura, a submariner with almost fifteen years’ experience in the silent service, who had joined the Sixth Fleet on September 5.

The Naval General Staff sent as representatives Fukudome and Tomioka and his assistants, Miyo and Sanagi. The latter would serve as chief umpire for the Pearl Harbor exercise.15 Of course, Uchida, with his special duties pertaining to operations against the United States, also attended. Likewise, Maeda, head of the Intelligence Bureau, came with his shrewd chief of American affairs, Ogawa. Nagano and Ito were conspicuous by their absence; although invited to attend, they never poked their noses inside the Secret Room.16

Not all these officers came to approve the Pearl Harbor venture summarily. The Naval General Staff representatives still were “highly skeptical about Yamamoto’s plan.” They “attended the Pearl Harbor exercises not as participants, but as spectators and observers—like businessmen who had to be sold by a salesman.”17 Yamamoto also had some high-pressure selling to do within his own Combined Fleet, notably to Nagumo, who saw big trouble awaiting his task force, and Kusaka, whose realistic mind found, countless obstacles to the success of the mission in addition to his belief that it would serve no constructive purpose.

But Yamamoto had powerful supporters. “All his officers were very loyal to Yamamoto, looked up to him, and were eager to carry out his plan,” Sasaki said.18 Of course, a cynic might point out that they would have to go along with him or be transferred in short order. But in general, Yamamoto preferred to earn his staff’s respect and affection rather than exact an impersonal, dutiful loyalty. Yamamoto could also count on his crony Yamaguchi and the latter’s eager air officer, Suzuki. And Genda would proclaim the true faith of Yamamoto’s creed with force and conviction.

Even at this time, with a tentative Pearl Harbor plan so far advanced that it could form the basis for a top-level table exercise, serious questions still urgently demanded appraisal. Of all these possible queries, the war games dealt with only two: Was the operation technically feasible, and could secrecy be achieved? Naturally the chart room exercises could not resolve these questions beyond cavil. The participants in the war games could hope to reach only an estimate of the probabilities.

One problem had to be resolved before the mock attack could start: What route should the task force choose? This provoked the first open disagreement in the Secret Room. Nagumo clung to the southern approach, but Yamaguchi, Sasaki, and Genda stoutly insisted that the northern passage would provide the shorter, more secure pathway to the target. Under this avalanche of contrary opinion Nagumo gave way reluctantly. His continual complaints against the northern approach formed an obbligato in minor key throughout the war games.19

Another split of opinion developed over the question of aerial reconnaissance. Yamaguchi wanted an extensive system of air patrols en route to Hawaii to scout in every direction for enemy ships, planes, or foreign merchantmen. Advance warning of possible detection could give the task force time to prepare for every conceivable emergency or even change its course.

This suggestion drew prompt protest from Genda. “It is too dangerous,” he declared. “Bad weather might cause the scouts to lose contact with their mother ships. This could lead to a crackup at sea when they ran out of fuel, and the enemy could spot the wreckage. Or a panicky pilot might tip off the task force’s presence by breaking radio silence. The enemy could detect patrol planes a hundred or so miles from their carriers, resulting in the same breach of security. Aerial reconnaissance will place the mission in gravest jeopardy from the outset.”

Yamaguchi, who knew the value of every scrap of last-minute information, and Genda, whose tactical plan was predicated upon secrecy, sparred enthusiastically over this problem. Nagumo offered no opinion. Each argument held much merit, and each contained almost equal danger. In the end Genda converted Yamaguchi, and so it was agreed: no air patrols en route.20

These questions resolved, the exercises began with a proposed X-Day of November 16. First to move out were Shimizu’s submarines, which left Japan theoretically on October 14, arriving at Wotje on the twentieth. They would leave Wotje between the twenty-eighth and thirtieth and by November 15 would encircle Oahu at a distance of some 300 miles.21

Meanwhile, Nagumo’s task force moved to its rendezvous in Akkeshi Bay far up on the eastern coast of Hokkaido. This remote bight was far enough north to lessen the problem of fuel supply and could provide some protection against discovery by American submarines. “During the war games and in the period following we made a concerted effort to keep the point of rendezvous a tight secret,” explained Genda. “For if this leaked out, the odds against Japan, which were already serious, would have become prohibitive.”22

This tentative task force consisted of the First and Second Carrier Divisions, two battleships, three cruisers, plus destroyers and tankers. No submarines accompanied the armada during these war games. Nagumo set force speed at about twelve knots course easterly, gradually veering southeast as he approached the target area.23 Refueling took place twice—on November 8 and 13. On the twelfth ships designated to watch out for fishing vessels moved into place ahead and astern, to port and starboard of the task force.

On the fourteenth Nagumo received word that the Red fleet was in Pearl Harbor as of November 11. From this point, increasing signs of American activity came into view. On November 14 Hawaii’s defenders were making aerial reconnaissance before sunrise, during the day and after sunset over a 400-mile radius. That same date the “Americans” spotted what appeared to be a submarine south of the islands.24 On the sixteenth—X-1 Day—Red Forces noticed oil on the surface, which could have leaked from submerged submarines,25 and expanded their search arc to 600 miles. Late that afternoon a scout plane found the task force, but the Japanese destroyed it before it completed its report.26

This apparently occurred shortly after Nagumo’s ships began their high-speed run at twenty-four knots toward Oahu.27 About this time Shimizu’s submarines reported ten enemy cruisers heading in Nagumo’s direction. Undaunted, he pressed on until he reached approximately 200 miles north of Oahu.28 There he turned his carriers into the wind and launched his first attack wave.29

The Blue strike force expected heavy resistance and got it.30 The Red team, operating from a room of its own, was under the direction of Kanji Ogawa. He had witnessed at least one American exercise during the 1930s of just such an attack against Pearl Harbor. Ably assisted by Captain Bunjiro Yamaguchi, who commanded the Red Army and Marine forces on Oahu,31 Ogawa had set up an excellent reconnaissance screen. And the scout whom the Blue team shot down had managed, after all, to convey a warning. Although the first wave had been launched without interference, over Oahu it encountered a swarm of Ogawa’s interceptors which kept it so busy fighting its way to the targets that it could not bomb effectively. At the same time ship guns and shore batteries blazed away at the attacking planes, dropping them like ducks over a hunter’s blind.

While all this action went on, Nagumo’s second wave droned down on Pearl Harbor an hour or so behind the initial force. But it had no better luck. Ogawa’s interceptors whizzed in and out of the attack formation which buckled under a hail of steel from Yamaguchi’s ground defenses. Half of Nagumo’s aircraft scrambled back to their carriers, having inflicted only minor damage to the ships in Pearl Harbor and the military installations on Oahu.32 Ogawa and Yamaguchi had given a graphic illustration of what the Japanese could expect if the Americans received a timely warning of the attack.

As the Blue remnants fled, Red bombers roared hard on their tails and rained upon the task force a shower of bombs, sinking two flattops and slightly damaging the other two as well as some of the support units. The remains of Nagumo’s ships escaped to the west. Damage to the task force about equaled previous Japanese estimates—roughly one-third of the armada.

Licking their paper wounds, the Blue Forces profited by their lessons—the efficiency of the Red air patrols plus the poor timing of the task force’s arrival on the scene of action.33 In the attempt to avoid the first and correct the second, the Japanese scheduled the second dry run so that the task force would arrive at a point approximately 450 miles north of Oahu at about sunset the evening before the attack. They estimated that Red aerial reconnaissance could reach out from Hawaii no more than 600 miles in any direction, giving the attackers a margin of safety. According to their calculations, sunset would find the American reconnaissance planes well on the way home from their outer patrol limit. Thus, the task force should have several hundred miles between it and the searching eyes of United States prowlers from Oahu.34

Of course, they realized that it would be quite a trick to stay in the safety zone, especially during daylight hours, no matter from what direction the Blue fleet approached Pearl Harbor. The planners knew, however, thanks to Yoshikawa, that the defenders could cover effectively only a radius of 180 degrees. For the most part they covered the area south and southwest of the great base, thus leaving the vital seaways north of Oahu inadequately patrolled.35

With these conditions in mind, Nagumo sailed on a more northerly course on the second trial run. He proceeded eastward to approximately 450 miles directly north of Oahu and arrived near sunset.36 The task force had now reached the position and period of greatest danger. Suppose some sharp-eyed American scout spotted it on the eve of the attack before darkness closed over it?

In their minds’ eyes the planners could see the picture all too clearly in view of the abortive first attempt. Long before Nagumo’s fleet had completed the high-speed run south to the launching area, the U.S. Pacific Fleet’s ships and aircraft would be storming northward in superior numbers to meet the invaders head-on. In the ensuing brawl Japan could lose the greater part of its carrier strike air power within an hour and be left with its entire war plan out of gear. Hence the excruciatingly careful calculations of time and distance.

Safe at the designated point, Nagumo began his high-speed run southward. From that moment good fortune had to sail with him. The blueprint allowed no margin for mechanical breakdowns, significant course adjustments, not even a storm at sea. If the task force could reach this predawn objective without detection, the scales should dip in its favor because at this hour American air patrols would scarcely be taking off. Therefore, if Nagumo’s first wave winged southward far enough before the enemy scouts started out, the attack would be a surprise. In that event chances for a successful strike would be excellent.37

On this second mock attack everything went smoothly. The invaders encountered no aerial or surface reconnaissance, and the Blue Forces quickly gained complete command of the air. Nagumo achieved all the surprise he could wish as his bombers swooped down on the Red fleet in harbor. Estimated damage to the enemy amounted to loss of four battleships and one severely pounded; the carriers Lexington and Yorktown sunk, with Saratoga seriously damaged; three cruisers sunk and three others with their fighting capability sliced in half. Red air strength on Oahu had been virtually broken, including fifty fighters shot down and eighty destroyed on the ground.38

The Blue Forces escaped with relatively minor damage. Red aircraft finally spotted Nagumo’s ships, sank one carrier, and halved the capability of a second.39 In exchange, Blue shot down another fifty Red planes.40 Then “the Japanese fleet escaped to the homeland and was divinely aided by a squall just in time to permit it to leave the Pearl Harbor area without serious damage.”41

A swift getaway, then, constituted a basic element of Nagumo’s strategy. The subject of repeated attacks against Pearl Harbor did not come up for discussion in the Secret Room, although Genda and Sasaki often talked about the possibility both before and after the exercises.42 Quite the reverse—many of the planners emphasized the idea of bringing Japan’s precious carriers back quickly and safely.43

No serious discussion of an attempt to occupy Hawaii took place during the war games.44 Nevertheless, the idea was intriguing. A month or so before the exercises Kuroshima had exchanged views on the subject with Yamamoto, Ugaki, and Watanabe. The prospect appealed to Watanabe, but Ugaki thought they would have enough problems in executing the aerial strike without adding an amphibious assault. Yamamoto agreed with him, readily seconding Kuroshima’s recommendation that Operation Hawaii should include no plan for invasion.45 Watanabe favored an all-out operation and did a little investigating on his own along that line during the war games, but he received no encouragement. Kuroshima flatly refused to consider it, and when Watanabe spoke to Yamamoto, the Commander in Chief cut the subject short. “The occupation of Hawaii was simply not a part of Yamamoto’s strategic thinking at the time,” as Watanabe put it in retrospect.46

Nor did the war games settle the vexing problem of how many carriers would be allocated to Nagumo’s striking force. Genda believed that every available flattop and plane would be none too many to ensure the best results. But the Naval General Staff refused to denude the Southern Operations of all carrier support. Three—four at the outside limit—must suffice for a possible strike against Hawaii.

Mikawa protested against receiving a mere two battleships. He contended that Hiei and Kirishima could not wage a successful fight if they met United States surface forces during the passage to Oahu, and he demanded two more heavy warships, preferably Kongo and Haruna.47 But eventually Takahashi insisted on these two fine vessels for his Third Fleet, and because the Southern Operation had priority, he got them.

So the war games in the Secret Room ended with the matter of carrier and battleship complements dangling in the air, along with submarine escort and reconnaissance. A number of technical questions noted earlier in this chapter remained to be solved. High among them loomed the refueling problem, held over to become the subject of a later staff study.48

This rehearsal of Operation Hawaii required only one day—September 16. The next morning the participants returned to the Secret Room for a postmortem on the Blue Forces’ tactics and to listen to various reports. The session lasted well into the afternoon, but no one debated whether or not the Pearl Harbor attack should be carried out.49 Instead, those present heard Oishi describe the Blue actions while Ogawa reported on the Red. Then Sanagi explained the results of the attack and his judgments as chief umpire.50

In the general discussion which followed, Kusaka requested “the exact air scouting radius of the enemy and location of his ships, together with the general situation within Pearl Harbor.” He also asked for a destroyer squadron of sixteen ships, preferably the Fourth, Sixteenth, Seventeenth, and Eighteenth Destroyer Divisions. Then he proposed that the Sixth Fleet be placed under the commander of the task force and finally that the Zero’s airspeed restriction of 280 knots be lifted.51 After the critique of September 17 the participants gathered for a dinner which ended the exercise covering Operation Hawaii. The full war games officially adjourned at 1730 on September 20.52