Operation A-GO Part I

Air Battle Of The Philippine Sea by John Hamilton (Naval History and Heritage Command)

With Admiral Isoroku Yamamoto’s death in April 1943 a successor to the command of Combined Fleet had to be chosen, and the man picked was Admiral Mineichi Koga. While not of the same caliber as Yamamoto, Koga was highly qualified. Though his policies varied little from his predecessor, he was thought to be more conservative, with a cooler temperament.

One of the first operational plans Koga became concerned with was the Z plan. This was prepared in May 1943 and envisioned the use of the Japanese Navy to counter U.S. naval forces threatening the Japanese outer defense perimeter. (This line extended from the Aleutians down through Wake, the Marshall and Gilbert Islands, Nauru, Ocean, the Bismarck Archipelago, New Guinea, then westward past Java and Sumatra to Burma.)1 When their position in the Solomons disintegrated, the Japanese modified the Z Plan by eliminating the Gilberts–Marshalls and the Bismarcks as vital areas to be defended by the Navy. They then based their possible actions on the defense of an inner perimeter (including the Marianas, Palau, western New Guinea, and the Dutch Indies).

Koga survived Yamamoto slightly less than a year. While retreating from Palau just before TF 58 attacked that anchorage at the end of March 1944, his plane disappeared en route to the Philippines. As great as Koga’s loss was, it was compounded by the loss and subsequent capture of a top secret Z Plan copy and its coding system. Koga’s chief of staff, Admiral Shigeru Fukudome, left Palau separately from Koga on 30 March. In his possession was the Z Plan copy. The two planes ran into a storm (which probably killed Koga) and Fukudome’s crashed just off Cebu. Fukudome was captured by Filipino guerrillas and his precious documents seized. Although the guerrillas soon were forced to give up their prisoner, the documents found their way to U.S. forces via submarine. They were a priceless find. After recovering Fukudome, the Japanese realized that their operations plan was compromised and a new one needed.

Admiral Shigetaro Shimada, Chief of the Naval Staff in Tokyo, immediately began preparing a new plan. Based on a preliminary draft by Admiral Koga, the plan was known as Operation A-GO, and it was under this directive that the Japanese fought the Battle of the Philippine Sea.

Before A-GO went into effect, however, another important change took place in the Japanese Navy. Though the Navy had been a world leader in carrier development, many of its top commanders were battleship or “Big Gun” adherents. However, by early 1944 these commanders had finally accepted the fact that the carrier was the new capital ship. With this realization came a change in fleet organization.

On 1 March 1944 the First Mobile Fleet (or as more commonly known, the Mobile Fleet) was organized under the command of Vice Admiral Jisaburo Ozawa. Joining the carriers in the Mobile Fleet instead of remaining in separate fleets were most of the first-string battleships, cruisers, and destroyers in the Navy. The Japanese had finally accepted the concept (adopted by the U.S. Navy almost two years earlier) of entrusting a task force including battleships and cruisers to the tactical command of a carrier admiral.

A month passed after Koga’s death before a new commander of Combined Fleet was named. He was Admiral Soemu Toyoda, a sarcastic, but brilliant and aggressive officer. He raised his flag on the light cruiser Oyodo, anchored in Tokyo Bay, on 3 May. Toyodo received the A-GO plan from Shimada the same day and immediately issued the general order for Operation A-GO.

As with so many of the previous plans, A-GO envisioned a “decisive” fleet action. This time the “decisive battle areas” were deemed to be the Palaus and the Western Carolines. It was in these areas that the Mobile Fleet, along with heavy land-based air, would be concentrated. If by chance the U.S. fleet attacked the Marianas, its ships would be pounced upon by land-based planes in that area. Then the enemy would be lured into the areas where the Mobile Fleet could defeat him. There “a decisive battle with full strength (would) be opened at a favorable opportunity. The enemy task force (would) be attacked and destroyed for the most part in a day assault.”

The framers of the A-GO plan were nothing if not optimistic: “As soon as the enemy is damaged, he will be pursued. The strongest air force that can be used will be immediately deployed at land bases and ceaseless air attacks will be waged day and night. . . . Complete success is anticipated.”

In conjunction with Operation A-GO, Admiral Shimada came up with a plan to use planes from the home islands. This plan was known as TO-GO. The land-based naval planes of First Air Fleet or Base Air Force were to have an important role in this plan. Prior to the “decisive” battle these planes were to destroy at least one-third of the enemy carriers. Deployment of these planes started 23 May and was completed by early June. However, because of the proposed battle area, the majority of the aircraft were stationed in the Carolines–Philippines area. Only 172 aircraft were based at the point of attack, the Marianas.6 However, a number of planes from the Hachiman Air Unit in Japan could be sent into the Bonins (including Iwo Jima) and thence south to the Marianas if danger developed there. Clearly, the Japanese placed a great deal of faith in their land-based planes for the coming action. However, though TO-GO was good theory, it failed miserably in practice.

The Japanese had every reason to hope, even to pray, that the “decisive” battle would be fought in the Palaus—Western Carolines area. They were running out of fuel for the Navy! Even though an enemy attack on the Marianas was not out of the question, there was not enough fuel for the Mobile Fleet to steam there and fight a battle. American submarines had recently been making Japanese tankers special targets and they had been doing very well at it. In the first five months of 1944 the U.S. subs had sent twenty-one tankers to the bottom. The oil Japan and her Navy so desperately needed was not reaching the Home Islands.

Oil was available to the Navy from the Borneo oilfields of Tarakan and Balikpapan—oil pure enough to be delivered unprocessed directly into the ships’ fuel bunkers. But this unprocessed oil was also highly volatile and therefore dangerous to use. Also, it contained some impurities that tended to foul boilers. For these reasons it was ordered that this oil be processed by refineries in Sumatra and Borneo before being issued to the Mobile Fleet.

Following the distribution of the A-GO plan, senior staff officers from all the concerned commands met on Saipan between 8 and 11 May. During discussions of the plan the disturbing question of a possible American attack on the Marianas came up. At first the high command ruled out the possible sortie of the Mobile Fleet to the Marianas because of the fuel situation. The nagging problem remained, however. Toyoda, therefore, decided to take the admittedly daring step of authorizing the use of unprocessed Borneo oil for the Mobile Fleet units. With this fuel the Fleet would now be able to give battle off the Marianas. But the use of this volatile fuel would have a serious effect on the Mobile Fleet during the Battle of the Philippine Sea. To be nearer the supply of oil the Mobile Fleet began congregating at Tawi Tawi in mid-May. This fine anchorage is on the westernmost island of the Sulu Archipelago, only 180 miles from Tarakan.

Ozawa’s own Carrier Division (CarDiv) 1, consisting of the fine new 29,300-ton armored-deck carrier Taiho, plus the veteran heavy carriers Shokaku and Zuikaku, sailed from Lingga Roads south of Singapore, where it had been training for over two months, on 11 and 12 May. (For the coming battle Ozawa would wear two hats: one as commander of the Mobile Fleet; the other as CarDiv 1 commander.) On the 11th CarDiv 2, comprising the 24,140-ton sister ships Junyo and Hiyo and the converted 13,360-ton Ryuho, and CarDiv 3, with the 11,262-ton Zuiho and the 11,190-ton former seaplane tenders Chitose and Chiyoda, left the Inland Sea. After fueling their destroyers at Okinawa, these two divisions proceeded to Tawi Tawi, arriving on the 16th.

The air units assigned to each carrier division were the 601st, 652nd, and 653rd Naval Air Groups. These were largely green organizations. The 601st had been shattered at Rabaul in November 1943 and, newly reformed, did not join CarDiv 1 until February 1944. The 652nd had also been smashed at Rabaul in January and was not reformed until March. Carrier Division 3’s 653rd Naval Air Group was an entirely new outfit, having been formed about the first of February.

These air groups were sorely lacking in training time, ranging between only two to six months. Training at Tawi Tawi for these inexperienced groups was hampered considerably by the lack of a suitable airfield there. Flight training had to be cancelled in May, and the air groups would consequently not be ready for the impending battle. An important factor in these units’ training was that most of the crews would be flying newer and “hotter” aircraft—D4Y Judy dive bombers, B6N Jill torpedo planes, and the improved Zeke 52 fighters. So, with its pilots lacking time in their new aircraft, combat experience, night qualifications, and coordination between (and within) their groups, the outlook for the air arm of the Mobile Fleet was not a happy one. And besides the lack of an airfield, there was another big disadvantage to Tawi Tawi—one the Japanese were to learn the hard way. It was easily accessible to submarines.

The movement of the Mobile Fleet to Tawi Tawi did not go unnoticed by the Americans. The capture of the Z Plan had already given intelligence officers of Vice Admiral Thomas C. Kinkaid’s Seventh Fleet an inkling of coming events. On 11 May they commented, “A powerful striking force is believed to be gathering in the northern Celebes Sea, using anchorages in the vicinity of Tawi Tawi. It is believed that the assembly of this force will be completed by 15 May.”

Although close to the facts, this was still just speculation on the Americans’ part. More hard evidence was needed. This evidence was beginning to trickle in, however. The submarine Lapon, patrolling off the west coast of Borneo, spotted at least three carriers, five cruisers, and a number of destroyers steaming by about six miles away on the morning of 13 May. The sub couldn’t get into an attack position but was able to send a contact report that evening.

Following the Lapon report, Commander Submarines Southwest Pacific (or in Navy lingo, ComSubSoWesPac) ordered the Bonefish, skippered by Commander Thomas W. Hogan, to take a look at Tawi Tawi. Hogan brought his sub south from the Sulu Sea, where he had been patrolling, at full speed. Early on the morning of the 14th Hogan spotted a convoy of three tankers and three destroyers. It appeared they were heading for Tawi Tawi. Creeping up on the convoy, Hogan fired five torpedoes from 1,300 yards. Two of them hit—one in a tanker and one in the 2,090-ton destroyer Inazuma, which went down. The remaining destroyers pounded the Bonefish for a time, but the sub was able to slip away.

A little before noon the next day, while the Bonefish was lying submerged some forty miles northwest of Tawi Tawi, a large group of ships passed by, headed for the anchorage. Possibly the force that the Lapon had seen, it contained one large carrier, two battleships, many cruisers, and about ten destroyers. Hogan got off a contact report that night.

Hogan was not finished looking over Tawi Tawi. The next day he moved in closer, raised his periscope, and saw a sight mouthwatering for a submariner: “Six carriers, four or five battleships, eight heavy cruisers, light cruisers, and many destroyers.”8 But the Bonefish had only one torpedo left, so this would remain but a tantalizing target. Hogan moved south during the night and sent out another report. Two enemy “tin cans” must have been listening, for they immediately came out after the Bonefish. Hogan took his sub deep, however, and was able to evade his attackers.

To help the Bonefish keep Tawi Tawi under surveillance, two more subs (the Puffer and Bluefish) were ordered into the area. While approaching Tawi Tawi on the morning of the 22nd, the Puffer, under the command of Lieutenant Commander Frank G. Selby, found a group of vessels on training maneuvers. Two flattops and three destroyers could be seen as Selby crept in. Carefully setting up on one carrier, Selby was startled when the other carrier swept by, only 500 yards astern. Breaking off the attack, Selby brought the Puffer around for another approach. Finally, at a range of 1,400 yards he fired a spread of six torpedoes. Although one, and possibly two, torpedoes hit the Chitose, they apparently were duds and did no damage to the carrier. All that Selby and the Puffer got for their effort was a good working-over by the escorts.

The Puffer made up for the attack on the Chitose by sinking two ships on 5 June. The 4,465-ton Takasaki and 7,951-ton Ashizuri were valuable ships designed to operate with the carrier forces, furnishing the flattops with supplies while at sea. They even provided aircrew quarters and aircraft repair facilities.

Another submarine, the Cabrilla, visited the Tawi Tawi area a few days after the Puffer’s action with the Chitose. During an attack on a group of three carriers and three battleships maneuvering outside the anchorage, the sub’s skipper apparently took too long a look at his targets. The sub was suddenly depth-charged by a plane, and was violently shaken up. The enemy vessels were able to retire safely to Tawi Tawi.

U.S. submarine operations in this area had been reasonably successful so far and were far from being finished. One important result of the subs’ attentions was that the Mobile Fleet’s maneuvers were curtailed considerably in the month before it sailed for battle. On the other hand, Japanese submarine operations during A-GO can hardly be considered successful. At least twenty-five enemy subs were used for scouting and supply purposes in the operation; seventeen were sunk. No useful information was obtained and not one American ship was even damaged.

The Japanese began their submarine operations on 14 May, the day the Bonefish moved into the Tawi Tawi area. Still convinced that an American attack would be aimed at the Palaus, the Japanese set up a scouting line (the NA line) of seven submarines starting at a point about 120 miles northeast of the Admiralties. Other subs were stationed in the Marshalls and Marianas area. The NA-line submarines were decimated by U.S. hunter-killer groups (particularly that of the England). Other Japanese submarines suffered equally poor results.

The I-176 was on a supply mission to Bougainville when it was pounced on by the destroyers Haggard, Franks, Hailey, and Johnston. After holding the sub down for about twenty hours, the destroyers began taking turns on attack runs. Following five separate attacks, the Franks began another run shortly after midnight on 17 May. A full depth-charge pattern was sown, and the unfortunate sub was blown up and sunk northeast of Green Island. One sub down. The RO-42, patrolling off Eniwetok, survived three salvos of hedgehogs (a type of throw-ahead projectile more accurate than the conventional roll-over-the-side depth charge) from the destroyer escort Bangust on 10 June, but could not survive a fourth. Two down. While steaming on the surface north of the Admiralties on 11 June, the RO-III was surprised by the destroyer Taylor. After taking numerous 5-inch and 40-mm hits, the Japanese boat crash-dived and was put under permanently by the “tin can’s” depth charges. Three down. On 16 June the destroyer escort Burden R. Hastings made contact with a surfaced submarine about 120 miles east of Eniwetok. The sub suddenly submerged, and the destroyer escort fired two hedgehog salvos followed by four depth charges. A violent explosion accompanied the second salvo, and the depth charges finished the job of breaking up the enemy vessel. At daylight an aluminum nameplate with RO-44 written on it was found. Four down.

In the Marianas the Japanese were no luckier. A picket line manned by the I-10, I-185, and I-5 was set up east of Saipan, but it did not last long. The I-5 simply disappeared, the I-185 was sunk by the destroyers Chandler and Newcomb on 22 June, and the I-10 came out on the short end of a battle with the destroyer David W. Taylor and destroyer escort Riddle on 4 July. Three more vessels had been crossed off the list of operational Japanese submarines.

On 13 June the destroyer Melvin met the RO-36 near Saipan and pelted the sub with 5-inch fire and depth charges. The destroyer Wadleigh, with help from the Melvin, sent the RO-114 down on the 16th. The next day a Liberator of VB-109, flying out of Eniwetok, bombed and sank the RO-117 cruising on the surface. Another surfaced submarine, the I-184, ran afoul of an Avenger from the escort carrier Suwannee on 19 June and never returned to Japan to report the attack. A total of eleven Japanese submarines had been lost so far. Six more were to be sunk during this period, and all six belonged to the destroyer escort England.

USS England: The Escort Destroyer

The England, commanded by Lieutenant Commander Walton B. Pendleton, was a brand-new ship with only about ten weeks sea experience. At Purvis Bay (on Florida Island across Ironbottom Sound from Guadalcanal) she was assigned to Escort Division 39 along with the destroyer escorts Raby and George. The officer in tactical command (OTC) was Commander Hamilton Hains, riding in the George. Armed with excellent information on the NA line provided by American codebreakers, the three ships left Purvis Bay on 18 May and headed north to attack the line. However, the first unfortunate to test the England’s inexperienced crew was not a member of the NA line, but a submarine on a supply mission to Bougainville. At 1335 on the 19th, the England picked up the sub (the I-16) on her sonar. Five hedgehog attacks were made with hits being made on the second and fifth runs. Following the last attack, a violent explosion threw men to the deck and lifted the England’s fantail out of the water. At first the England’s crew thought they had been torpedoed; then they realized the I-16 had blown up.

Early on the morning of the 22nd the three destroyer escorts ran across the RO-106 cruising on the surface. The Japanese submarine dove, but it could not escape. When the George’s first attack was unsuccessful, the England took over and sent the enemy submarine to the bottom with two hedgehog salvos. Twenty-four hours later the RO-104 became the quarry. Detected on the surface, she plunged and then played cat and mouse with the Raby and George. As the hunters closed the wily submarine skipper “pinged” back at his “pinging” attackers, hoping to foul up their runs. He also maneuvered his vessel skillfully. The Raby spent over half an hour in fruitless attacks, and the George made five runs without hitting anything. Finally tiring of the game, the OTC ordered the England in. Her first pass was unsuccessful but on the second her hedgehogs tore the RO-104 apart. Shortly after this action another enemy submarine was detected, but this one was lucky; it escaped.

By this time Commander Charles A. Thorwall, commanding Escort Division 40 and riding in the England, was ready to change the England’s call sign from “Bonnie” to “Killer-Diller.”

Moving south toward Manus, the three little ships had still more excitement ahead for them. A little after midnight on the 24th the George’s radar locked onto a surface target, range 14,000 yards. The target submerged, but at 0150 sonar contact was made. The captain of this sub was good, too—but not quite good enough. The England was forced to make two dry runs because of shrewd evasive tactics by the enemy skipper, but the third pass scored. At least three hedgehogs hit and only bits and pieces of the RO-116 surfaced again.

On 25 May this crack hunter-killer group received orders to proceed to Seeadler Harbor in the Admiralties, to refuel and load more hedgehogs. At 2303 the Raby’s radar picked up another sub 14,000 yards away. Within minutes the other two ships also had the target. When the range closed to 4,000 yards the sub dove. Sonar contact was quickly made, and the Raby was given first chance this time, but she muffed it. The England didn’t. Her first salvo snuffed out the RO-108’s life some 250 feet below the surface. At daybreak oil and debris were discovered gushing to the surface.

Arriving at Seeadler Harbor on the afternoon of the 27th, the three ships loaded more hedgehogs from their sister destroyer escort, the Spangler, which now joined them. After fueling, the four ships sortied the next afternoon to join a hunter-killer group built around the escort carrier Hoggatt Bay. Escorting the carrier were the destroyers Hazelwood and McCord.

Early on the morning of the 30th, as the task group was steaming north, the Hazelwood made radar contact with the RO-105. The destroyer forced the sub to dive, but a depth-charge attack gave no conclusive results. The Hazelwood maintained contact until 0435 when the Raby and the George arrived to assist. The two destroyer escorts were asked to make attacks while the McCord acted as contact keeper. (These two destroyer escorts were still part of Escort Division 39, while the England and the Spangler were now Escort Division 40 under the command of Commander Thorwall.) By now the other destroyer escorts were getting an inferiority complex, so Commander Hains was trying to give them a chance at a kill. The Raby and George each made a number of passes over the unlucky RO-105 and several explosions indicated the sub was hit. But it was apparently only wounded. The two ships spent the rest of the day holding the RO-105 down.

Shortly after the sun dipped below the horizon, the Americans heard three heavy underwater explosions. No debris or oil floated to the surface, so it was thought the Japanese skipper had become cagy and had fired torpedoes to throw his pursuers off the track. The ruse did not work, for contact was soon regained and maintained the rest of the night. By now the task group really wanted this submarine, but it was decided to wait until daylight to make any more attacks.

When dawn broke the George, followed by the Raby and Spangler, attacked. They all missed. Time was growing short, for the ships had received word to clear the area, as they might get jumped by enemy planes. Finally, the OTC called in the England. This young “old pro” did not miss. At 0729 on the 31st her sonar operator reported contact with the sub. Six minutes later a full salvo of hedgehogs connected with the enemy vessel. A huge explosion followed and the RO-105 went down for the last time. Only an oil slick and a few pieces of debris marked her passing.

Six Japanese submarines had been sunk by the England in thirteen days. It was a masterful performance which earned the ship a Presidential Unit Citation. Commander Thorwall congratulated the England and her crew with the comment, “As a result of your efforts Nip recording angel working overtime checking in Nip submariners in joining Honorable Ancestors.”

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