The Saipan Mission – Plan for a “Special Attack of IJN Battleships”

The disastrous Philippine Sea battle left the Imperial Navy in the position of having important forces in a combat zone completely dominated by the Allies. Not only were more than 15,000 sailors caught in the trap, but also those endangered included skilled ship artificers and aircraft mechanics, Japanese communications intelligence experts, naval infantry, and the staffs and commanders of the Central Pacific Area Fleet, First Air Fleet, and Sixth Fleet.

For days, talk of rescue expeditions roiled across Tokyo. Navy staff officials promised salvation. Junior naval officers clamored for action, accusing the Japanese Army command of obstructing a rescue. Many others thought the whole idea ludicrous. The scheme might have had some chance while Ozawa’s Mobile Fleet monopolized Allied attention, but the day after Prime Minister Tojo approved the mission the Mobile Fleet went down in defeat at the Turkey Shoot.

Combined Fleet chief of staff Kusaka Ryunosuke, anxious to succor his old boss Nagumo, dreamed up the first scheme for the Saipan mission, revolving around two old battleships. Staffers thought Kusaka’s idea silly, but he was determined to go ahead. Captain Yamamoto Chikao (no relation to the great admiral), who led the operations section of the NGS, completed the plan on June 21.

The next day Admiral Ozawa’s vanquished Mobile Fleet anchored at Okinawa on its way home. As the fleet neared Japan, C-in-C Toyoda Soemu held the options open by ordering Ozawa to concentrate in the Inland Sea and prepare for an immediate mission. Under a revised rescue plan, the one available fleet carrier, Zuikaku, and every other two-bit aviation ship the Navy could scrape up would be loaded with whatever planes could fly, scrounged from both the Army and the Navy. The planes would have to take off only once. They would be expended in the fight.

This improvised carrier fleet would sail several days behind a convoy escorted by the Fifth Fleet, Japan’s northeast sea frontier protection force, expected to leave the port of Yokosuka carrying an Army infantry regiment. The carrier force would cover its approach with a one-way air attack. The next day Japan’s Second Fleet, the Navy’s big-gun unit, would steam in and crush the Allied fleets off the Marianas. The Fifth Fleet would then arrive with the Army’s regiment, and a day after that would be another convoy with a full Army division.

The rescue, still merely on paper, already looked shaky. The Ozawa fleet had been smashed in a full-scale battle and could hardly be ready for another. That went for the Second Fleet as well—it had been part of Ozawa’s force. Admiral Ozawa himself estimated he needed two months to get the ships back in fighting trim. About the only naval units really at hand were the Fifth Fleet and the old battleships. The aged Yamashiro of Battleship Division 2, and a pair of converted battleship–aircraft carriers, the Ise and Hyuga, were just completing modification to this hybrid status. There was also the Fuso, then in the southern Philippines after participating in a similar—but abortive—sortie to aid the Japanese defenders of Biak Island. The two hybrid ships, still working up, were ultimately left out of the plan.

Operations officers wanted to send at least the Yamashiro. She could dash to Saipan, deliver the regiment to stiffen the defenses, and then ground herself to serve as an artillery battery. The Army might contribute one of its own transport ships. Cruisers of the Fifth Fleet could carry more troops as well as the landing barges to put them ashore. With a handful of escorts these warships could become a relief mission. The Fuso, sailing independently, would shoot up Allied convoys headed to the battle areas. Combined Fleet alerted her for that mission on June 17. But the battleship-only rescue was a nonstarter. Three days later the Navy scrubbed the Fuso raiding mission. Combined Fleet commander in chief Toyoda Soemu thought the entire concept reckless and rejected chief of staff Kusaka’s proposals. According to Kusaka this was among the few times Toyoda ever did that.

Historian Anthony Tully attributes the rescue to Captain Kami Shigenori. A notorious hothead in the Imperial Navy, Kami might well have dreamed up this kind of scheme. Tully reports that Captain Kami, ready to accept any risk, volunteered to skipper the Yamashiro to her destiny. Contrary to some claims, however, at that time Kami was no operations specialist with either the fleets or the NGS. He was captain of the light cruiser Tama. That vessel at least belonged to the Fifth Fleet and could have participated, but it leaves the captain as just another advocate, not the planner of this extravaganza. It is true that Kami had spent much of his career in staff billets, but by the same token he had minimal command experience. The Tama had been his first ship in many years. Why the Navy should put Kami in charge of a battlewagon goes unexplained. In November 1966, Admiral Kusaka personally claimed credit, regretting the rescue had not been carried out, claiming that with the right timing it could have worked.

Meanwhile the plan had also envisioned that a long-range air unit (the “Hachiman Force”) would cooperate with the surface fleet, flying out to strike the Allied armada and paving the way for the surface ships. Cobbled together ad hoc, and composed of crews picked from the Yokosuka Air Group and Twelfth Air Fleet, the Hachiman Force actually deployed to Iwo Jima, but it never comprised more than sixty aircraft, and half those were lost in June and July.

Serious fliers thought this enterprise could only be a death ride. How a small air unit would penetrate the dense Allied umbrella, where the entire Mobile Fleet had failed, remained a mystery. Similarly, an ancient battleship was supposed to sink the mighty Blue Fleet, and another would get through to Saipan and reverse the strategic balance. The rescue plan had no substance. Admiral Toyoda stuck to his guns, and the Army high command dismissed the idea out of hand. The Army had spent six months reinforcing the Marianas with really significant forces—more than a few of which had been sunk en route by Allied subs. A single regiment sent now would achieve nothing, a regiment plus a division not much more.

But these plans, empty as they were, are important for other reasons. Such a degree of desperation now prevailed in Tokyo that the most extreme alternatives suddenly appealed. There is an argument from cultural history that the Japanese held special esteem for showing nobility even in failure. In the Pacific war in late 1944, Japan stood at the brink of that very deep chasm.

A more mundane reason would turn out to be a distraction in the next real battle. That is, the rescue plan envisioned taking the Fifth Fleet away from its geographic mission, employing it instead as an integral element in a battle concept. Once the Imperial Navy finally finished reconfiguring the force for the next battle, that element stuck—the old northern force would morph into the anticipated vanguard for the Ozawa fleet.

Emperor Hirohito sided with the young Navy officers. He demanded action. He had told Admiral Shimada on the eve of the Philippine Sea battle that with sufficient determination Japan might achieve a success like Tsushima, the glorious 1905 victory against the Russian fleet in the Sea of Japan. Hirohito warned Prime Minister Tojo of air raids on Tokyo if the Marianas were lost. They had to be held. IGHQ chiefs kept bringing him bad news. The emperor ordered Navy minister Shimada to craft a rescue. On June 24 Tojo and Shimada united to tell the emperor the bad news that Combined Fleet now felt the plan unworkable. Hirohito countered, demanding a second opinion from the Board of Field Marshals and Fleet Admirals, a military appendage of the jushin, or senior statesmen, who had a behind-the-scenes role in Tokyo. When the board also nixed a rescue, the emperor ordered them to put that judgment on paper, turned on his heel, and stalked off. The Yamashiro mission evaporated.

One jushin with whom diplomat Kase Toshikazu discussed Japan’s situation was Admiral Okada Keisuke. Okada had been Navy minister and prime minister in the 1930s. Now he told Kase that a rescue operation would only deepen the disaster, though perhaps that was a good idea—“he thought it advisable to let the ‘young fellows’ have their own way once in order to reconcile them ultimately to their inevitable fate—defeat.” Admiral Yonai Mitsumasa, another jushin, agreed the loss of Saipan would be a calamity, but he refused a useless gesture.

On June 29 Prince Takamatsu conceded to associates that the recent defeat had stymied the Imperial Navy for the present. The Navy captain’s remark, coming from the second brother of Hirohito, suggested the emperor had accepted reality.

The only efforts to rescue the Japanese in the Marianas would be by submarine. The big fleet submarines, I-boats, and smaller medium-range craft, RO-boats, were used in these operations. Two subs went down in futile missions to Saipan to recover Sixth Fleet commander Vice Admiral Takagi Takao. Thirteen Japanese submarines were lost in the Marianas, nearly half in rescue attempts. The sole success came to Lieutenant Commander Itakura Mitsuma’s I-41. Itakura managed to get his boat into Apra Harbor on Guam and spirit away more than 100 airmen.

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