'A' was the Japanese naval counter-offensive against the US 'Forager' amphibious invasion of Saipan in the Mariana islands group leading to the 'Battle of the Philippine Sea' (15/20 June 1944).

Admiral Isoroku Yamamoto, commander-in-chief of the Combined Fleet, had been killed on 18 April 1943 in the US 'Vengeance' air operation, and on the following day Admiral Mineichi Koga had been appointed to succeed him. Like his predecessor, Koga wished to maintain the Imperial Japanese navy’s long-held desire to engage and defeat the US Navy’s major Pacific strength in a battleship-dominated 'decisive battle' at a time early in 1944.

From the very start of the Pacific War on 7 December 1941, the Japanese war plan had been to discourage and dishearten the USA by inflicting on the latter’s military forces losses so severe that the US public would become war weary and the US government would become convinced of the need to sue for peace on the basis of a status quo allowing Japan to keep the conquests it had achieved in east and south-east Asia. Though at a numerical disadvantage from the outset, and hampered by an industrial disparity which could only exacerbate that disadvantage the longer the war lasted, the Japanese high command believed the Imperial Japanese navy could engage the US Navy in a single but decisive engagement, known as the 'Kantai Kessen', in which the Japanese surface fleet would defeat the US Pacific Fleet in a totally decisive manner. However, the ability to fight and win such a battle was steadily slipping away from the Japanese. Imperial Japanese navy aircrew losses in the earlier attle of the Coral Sea' carrier engagement (resulting from 'Mo' and 'Re') and in the Battle of Midway' carrier engagement (resulting from 'Mi'), together with those of the lengthy Solomon islands campaign of 1942/43, had greatly weakened the Imperial Japanese navy’s carrierborne air power capability.

As the Solomon islands campaign was fought largely, in matériel terms, by the Imperial Japanese navy, the service’s losses in that campaign drastically reduced the number of skilled carrier pilots available to man the carrierborne air groups. On the other side of the coin, however, the losses suffered in the Solomon islands campaign by the US Navy could readily be absorbed, replaced and made good if not actually enlarged in a manner impossible for the Japanese. Thus it took the Japanese nearly a year to rebuild their carrierborne air groups, and then to only a mediocre quality, after the end of the end of the Solomon islands campaign.

The Imperial Japanese navy’s initial plan at this time was to seek and secure a massive engagement with the US Pacific Fleet early in 1944, more specifically whenever the Americans launched their next offensive, but the much-desired and much-anticipated 'decisive battle' had then to be delayed on several occasions. US matériel production capacity, aircrew training and technological advances meanwhile rendered any Japanese victory increasingly difficult to achieve. By the end of 1942, the Allied navies had overcome most of the technological advantages which Japan’s ships and warplanes had held at the start of the war. Furthermore, by the middle of 1943 mass production of ships and improved aircraft began to tip the balance of forces in the favour of the Allies, and this tendency was complemented by the adaptation of the Allies' training practices to meet new developments. The US revised fleet operations, with parallel developments in both the ships' combat information centres and in doctrine, training, and practices to get the most out of the new communications and sensor technologies.

After breaking through Japan’s 'outer' defensive ring in the costly 'Galvanic' offensive in the Gilbert islands group (including 'Longsuit' or the 'Battle of Tarawa') in November 1943, the US Navy brought a host of these improvements together in the form of the Fast Carrier Task Force under the command of Vice Admiral Marc A. Mitscher (known as Task Force 58 when part of Vice Admiral [from 21 February 1944 Admiral] Raymond A. Spruance’s 5^th Fleet and Task Force 38 when part of Admiral William F. Halsey’s 3^rd Fleet). Led by this main strike force, early in 1944 the US Navy continued its advance in a steady progression across the islands of the central Pacific. After achieving their goals in the Gilbert islands campaign, the Americans began a series of softening-up missions aimed at weakening Japanese land-based airpower in order to limit Japan’s ability to interfere with future amphibious invasions. In fact few of the US commanders realised how capable and powerful the Fast Carrier Task Force had become in real strategic terms. Though initially undertaken with perhaps too acute a sense of caution, the raids proved to be successful beyond anything US planners had foreseen. This was especially true of the 'Hailstone' precursor to the 'Catchpole' assault on Eniwetok atoll within the 'Flintlock' offensive against the Marshall islands group: 'Hailstone' effectively neutralised the primary central Pacific base of the Imperial Japanese navy in the lagoon of Truk atoll in the Caroline islands group, and in the process wholly changed the fashion in which the war in the Pacific Ocean would then be prosecuted.

While US commanders in general, and Spruance in particular, were highly concerned about the possibility that the Japanese might be able to attack US transport shipping and newly landed amphibious forces, the Japanese objective, in accord with the 'Kantai Kessen' concept, was actually to engage and defeat the Fast Carrier Task Force. Japanese commanders saw the Mariana islands group in the central Pacific, including Guam, Tinian and Saipan, as a key element of their 'inner defensive perimeter', for land-based fighter and bomber aircraft from these islands controlled the sea lanes to Japan and protected the home islands. As the Americans prepared for the Mariana islands campaign, the Imperial Japanese navy decided that the 'Kantai Kessen' could no longer be delayed.

The Japanese possessed a number of advantages which, they hoped, would turn the forthcoming battle in their favour. Though outnumbered in ships and carrierborne aircraft, they planned to supplement the latter with land-based aircraft. In addition, the Japanese aircraft had superior range, which could allow them to engage the US carriers beyond the attack range of US warplanes. Moreover, with island bases available in the area, the Japanese hoped to launch their attack forces at distance so that their aircraft could attack the US fleet and then land on island airfields to refuel and rearm. They then could shuttle back toward their parent carriers and attack the US ships once again in the course of these return flights. Thus the US ships would be in the position of having to take punishment from the air without being able to deliver it any realistic counter blow. Lastly, the area was dominated by the easterly trade winds. The naval aircraft of the era needed a headwind blowing across the flightdeck for take-off, and the easterly trade winds which predominated in the central part of the Pacific meant that aircraft carriers had necessarily to steam to the east in order to launch and recover aircraft. This meant that a fleet located to the west of the Mariana islands group would be in position to initiate and break off the battle, placing the initiative in the hands of the Japanese.

On 31 March 1944 Koga was killed when the aeroplane in which he was a passenger flew into a typhoon and crashed. The new commander-in-chief of the Combined Fleet was Admiral Soemu Toyoda, who continued the current work, finalising the Japanese plan as 'A'. This was adopted early in June 1944, then within weeks quickly put into place to engage the US fleet now detected heading for Saipan at the start of 'Forager'.

The Philippine Sea is a region of the western part of the Pacific Ocean bounded by Japan to the north, the Bonin islands group to the north-east, the Mariana islands group to the east, the western part of the Caroline islands group to the south, the Philippine islands group to the south-west, the large island of Formosa to the west, and the Ryukyu islands group to the north-west. This was the location of the last major carrier battle of the Pacific war, which took place when Toyoda activated 'A' to counter the US forces committed to the 'Forager' invasion of the Mariana islands group in June 1944. Because the US submarine blockade had crippled the Japanese tanker fleet, the Japanese were forced to base their main surface forces close to their sources of fuel in Borneo. The Japanese plan therefore called for a decisive battle to be conducted near the Palau islands group, where Vice Admiral Jisaburo Ozawa’s 1^st Mobile Fleet was to engage and destroy the Americans with the assistance of land-based aircraft. Should the USA attempt instead to fall on the Mariana islands group, the plan called for the US naval forces to be attacked only by land-based air power and lured to the south into waters more favourable to the Japanese plan.

As it became clearer that the Mariana islands group was the probable US target, threatening a complete interdiction of deliveries of refined furnace oil from the 'Southern Resources Area' to the Japanese home islands, the Imperial Japanese navy took the dangerous step of authorising the use of unrefined Borneo oil as bunker fuel. This was a measure of desperation as while Borneo oil is of a quality high enough to burn directly in ships' furnaces, it contains sulphur in quantities sufficient to render boiler tubing brittle, and also possesses enough in the way of volatile elements to be dangerously flammable. The use of unrefined Borneo oil reduced the need for tankers, however, and made it possible for the fleet to operate at a considerably greater distance from its more standard sources of fuel, thereby bringing the Mariana islands group within range for a fleet action.

Even so, the Japanese continued to hope that the US forces would strike farther to the south, and this was reflected in their aircraft dispositions: by a time early in June, the Japanese had four aircraft on Chichi Jima, 35 on Saipan, 67 on Tinian, 70 on Guam, 67 on Truk, 40 on Yap, 134 in the Palau islands group, 25 at Davao on Mindanao island in the southern part of the Philippine islands group, 40 in Cebu in the Visayan islands group of the central part of the Philippines, 42 on Halmahera, and 16 in the western part of New Guinea. Additional aircraft were available in the home islands and the other islands of the Japanese-occupied Netherlands East Indies to be staged into the operational area once 'A' had been activated, for a total of about 500 land-based aircraft potentially available for the 'decisive' battle.

The Japanese conducted a number of teishin (daring) reconnaissance missions in the period between late May and early June, and these provided a moderately accurate picture of US dispositions. A reconnaissance flight on 27 May from Truk atoll staged through Buin in the Solomon islands group to Tulagi at the south-eastern end of this island chain and gathered accurate intelligence on Rear Admiral Richard L. Conolly’s Southern Attack Force. Another two aircraft staged from Truk atoll through Nauru island to reconnoitre the fast carrier forces at Kwajalein and Majuro atolls in the Marshall islands group. This collation of all such information combined to point to an attack on the Mariana islands group, but the Imperial General Headquarters was currently preoccupied with the US 'Horlicks' landing on Biak island toward the north-western end of New Guinea as this threatened airfields important to 'A'. The resulting 'Kon' failed in its first two attempts to effect the relief of Biak, and the third attempt was cancelled when Toyoda learned of the US carrierborne air attacks on Saipan island during 11 June, and this in fact served finally to convince the Japanese leadership that the Mariana islands group was in fact the next US target. As noted above, it was on 12 June that Toyoda activated 'A', and on the following day Ozawa sortied his forces from Tawi-Tawi in a movement which was immediately spotted and reported by the submarine Redfin.

Part of the Japanese overall plan called for the deployment of a large number of submarines across all of the possible US approaches to the Mariana islands group. This effort was almost entirely unsuccessful, as a result largely of of the efforts of Allied code-breakers, and no fewer than 14 of the submarines were lost and not one Japanese submarine was in position to influence the subsequent fleet action.

In overall terms, therefore, the Japanese had started to develop 'A' after the US successes in the 'Galvanic' seizure of key parts of the Gilbert islands group in November 1943, and the 'Flintlock' and 'Catchpole' seizures of key parts of the Marshall islands group in the period between November 1943 and February 1944. The Japanese rightly concluded that combination of these three operations confirmed the primary axis of Admiral Chester W. Nimitz’s Pacific Ocean Areas command as being directed to the east or slightly to the north of east, and that its next objective would therefore in all probability be the Palau or Mariana island groups.

Given these strategic and geographical factors, therefore, the Imperial Japanese navy conceived 'A' within the context of its long-sought but in fact strategically impossible now actually irrelevant 'decisive battle' of the naval war in the Pacific. Koga and Toyoda both appreciated that the USA’s next forward move would take its forces to the Palau or Mariana island groups, on the strategic doorstep of the Japanese home islands. The capture of these island group, and more especially the comparatively substantial islands of the Marianas group, which offered good anchorages as well as the major asset of large areas of land suitable for the construction of major air bases and the concentration of troops and matériel, would give the US forces the opportunity to strike variously at the Japanese home islands, or Iwo Jima in the Bonin (Volcano) islands group, or Okinawa in the Ryukyu islands group, or the major island of Formosa off the coast of China. The successful implementation of any or all of these options would effectively sever Japan’s maritime links with the Japanese-occupied Philippine islands group and South-East Asia, together with all the strategically and industrially vital raw materials of the 'Southern Resources Area' of the 'Greater East Asia Co-Prosperity Sphere'.

Based on Koga’s preliminary 'Z' (iii) plan for the use of Japanese air and naval forces to destroy the US forces as they approached the Mariana islands group, Toyoda’s 'A' was promulgated in an operational order on 3 May, and called for the US invasion forces operating off the Mariana islands group (in the event Spruance’s 5^th Fleet with Vice Admiral Richmond K. Turner’s 5^th Amphibious Force and Mitscher’s Task Force 58 of fast aircraft carriers) to be attacked by powerful surface forces moving from the Japanese navy’s south-western base areas close to vital oil supplies.

Between 11 May and 12 June, the Japanese undertook significant preparations for 'A'. The first step, on 11/12 May, involved the movement of Ozawa’s 1^st Mobile Fleet in two groups from Lingga Bay in the Riau archipelago between Singapore and Sumatra, where Ozawa’s own 1^st Carrier Squadron had been training its pilots, to Tawi-Tawi, the westernmost island of the Sulu archipelago to the south-west of Mindanao island. Here the 1^st Carrier Squadron was joined on 16 May, the day after its arrival, by Rear Admiral Takaji Joshima’s 2^nd Carrier Squadron and Rear Admiral Sueo Obayashi’s 3^rd Carrier Squadron, the super-battleship Musashi and other units which had departed Japan on 12 May. The first Japanese losses then occurred as a result of US submarine attacks as the ships exercised in the waters around Tawi-Tawi: on 22 May Bonefish spotted and reported the fleet, and hit the light carrier Chitose with two torpedoes which failed to explode; on 24 May Gurnard sank the oiler Tatekawa Maru; and on 3 June Puffer sank the oilers Takasaki and Ashizuri. During 'Kon', the destroyer Kazegumo was sunk on 3 June by the submarine Hake, and on 8 June the destroyer Harusame succumbed to air attack.

Ozawa now had under his command the 1^st Mobile Fleet divided into three surface warship forces 1 supported by only a small fleet train. Also available, largely for scouting purposes, were no fewer than 24 submarines 2 of the Submarine Force of Admiral Takeo Takagi’s Saipan-based 6^th Fleet.

The Americans were fully aware of what the Japanese were planning, for Filipino guerrillas had passed on details of the Japanese plan after recovering a copy of this from one the senior staff officers of Vice Admiral Shigeru Fukodome, Koga’s chief-of-staff and like his superior officer a casualty, albeit surviving, of the air crash on Cebu island on 31 March.

As noted above, the Japanese navy had wanted its 'decisive battle' to be fought much farther to the south-west for two compelling reasons. Firstly, the US submarine arm’s successes against Japan’s merchant tanker fleet had led to a shortage of refined oil, with the result that when 'A' was launched the Japanese navy lacked sufficient refined oil to fight effectively at a radius as great as that to the Mariana islands group and, as noted, had therefore decided to use unrefined Borneo oil. Secondly, the Japanese had realised that the disparity between the US and Japanese fleets was so great, measured in ship numbers, the quantity of advanced warplanes and the availability of experienced carrierborne aircrews, that the latter would have to be aided to a great extent by land-based warplanes in securing a successful outcome in the 'decisive battle'. 'A' had been planned with this necessity in mind, but battles must be fought largely when and where the opportunity occurs, however, and the opportunity manifested itself in the Philippine Sea on and after 15 June.

The forces available to the Japanese navy for this eventuality had resulted from the reorganisation of the Imperial Japanese navy on 1 March 1944 into a 1^st Mobile Fleet 1 under the command of Ozawa, who was faced with the enormously taxing problem of establishing the conditions which would reduce the US forces' numerical and technical superiority to the degree that would to allow the Japanese to emerge victorious. His definitive version of 'A', therefore, was based on the premise of catching the US carrier forces operating to the west of the Mariana islands group in a location permitting them to be caught in a tactical vice between Japanese carrierborne aircraft operating from ships still farther to the west, and Japanese land-based aircraft operating from the island airfields of Guam and Rota to the east and Yap to the south.

The Japanese fleet and its aircraft were considerably weaker in numerical terms than those of the Americans: while the latter had seven fleet carriers and eight light carriers, the former could deploy five fleet carriers and four light carriers. The Americans were also superior in every other category of ship but heavy cruisers. The Americans had an overwhelming advantage in carrierborne aircraft, with 908 aircraft embarked, compared with 430 aircraft embarked on the Japanese carriers. However, the Japanese aircraft did possess a considerable range advantage, being able to scout to a radius of 645 miles (1035 km) as against 400 miles (655 km) for the US aircraft, and to attack at 345 miles (555 km) as against 230 miles (370 km). Moreover, Ozawa’s ships would be steaming into the wind and thus able to conduct flight operations while closing with Spruance’s vessels. Ozawa therefore planned to launch his carrierborne aircraft from outside the range of US counterattacks, and have them fly onward to Guam, where they would refuel and rearm, effectively doubling their attack value as the aircraft attacked the US ships on their flights back to the Japanese carriers. However, this capability could be gained only at the expense of increased aircrew fatigue during the long two-way flights to their targets.

The advantage on which Ozawa counted most heavily was the proximity of Japanese airfields, particularly those on Guam, Rota and Yap islands. As noted above, Ozawa believed that he could count on the support some 500 land-based aircraft, which would have given him a slight numerical advantage over the Americans. It was here that the Japanese plan first began to unravel, for by the eve of battle on 18 June, the warplanes of Vice Admiral Kakuji Kakuta’s land-based 1^st Air Fleet had accomplished almost nothing while also suffering heavy casualties and damage to their bases.

At this time the Japanese were beginning to equip their carrierborne air groups with more modern attack aircraft, most notably the Yokosuka D4Y 'Judy' single-engined dive-bomber and Nakajima B6N 'Jill' single-engined torpedo bomber. However, many of the carrier air groups still included significant numbers of the older Aichi D3A 'Val' single-engined dive-bomber, which was too slow to keep formation with the newer aircraft types.

The most important handicap suffered by the Japanese was the poor training of their aircrew. The US pilots who fought in the battle all had at least two years of training and 300 hours of flying time. But the Japanese had never been able to rebuild their air groups following their heavy losses in the Battle of Midway and the long Guadalcanal campaign. The pilots of the 1^st Carrier Squadron, which was deemed the best available to Ozawa, averaged just six months of training, while those of the 3^rd Carrier Squadron averaged only three months and those of the 2^nd Carrier Squadron just two months. The training of these pilots had been further hampered by the decision to relocate the carrier force to Tawi-Tawi in the months before the battle: this area lies so close to the equator that there were no trade winds to enable the slower carriers to get enough headwind over their decks to launch the most modern carrierborne aircraft. In overall terms, therefore, the Japanese aircrew were in every respect inferior to those of the Americans.

Given the fact that the Americans would not yet have had the time to secure on the Mariana islands group any lodgement large enough to allow the basing of aircraft, the US Navy would have to depend exclusively on carrierborne aircraft and, as noted, Japanese carrierborne aircraft typically possessed a range some 240 miles (385 km) greater than that of their US counterparts. So Ozawa planned to operate his carriers out of the reach of US carrierborne aircraft but within the range over which his own warplanes could attack: they would strike at US carriers which, according to the plan, would already have been damaged by Japanese land-based aircraft, then fly onward to land on Guam, where they would be refuelled and rearmed before taking off to attack the US carriers for a second time on their way back to their own carriers.

As is so often the case in military and naval affairs, however, the later reality differed radically from the earlier concept. The Japanese land-based aircraft failed to damage TF58, although Kakuta, located on Tinian island and commanding the Base Air Force (a component of Kakuta’s own Pacific-wide 1^st Air Fleet) on the Mariana islands group, nonetheless assured Ozawa that his 300 or so land-based aircraft had inflicted on TF58 losses great enough to bring about a virtual Japanese and US equality in ships and aircraft. But in fact Spruance had previously ordered carrierborne air raids on Iwo Jima and Chichi Jima, the staging areas essential for any Japanese aircraft heading toward the Mariana islands group, during the 15/17 June period, and the airfields of Guam and Rota had lost almost all of their aircraft and suffered crippling damage to their facilities to almost continuous US attacks from 12 June. Thus the battle would be fought solely by carrierborne aircraft, although Ozawa did not know that this had been the case until after the battle’s end, for Kakuta failed to admit the fact.

Spruance’s primary concern was that Ozawa would try to slip around one of TF58’s flanks and thus be in a position to fall on the vulnerable invasion transports and their escorts in the waters off Saipan. But all that Ozawa intended, with the aid of land-based air power, was to create and win the 'decisive battle' against the US carriers. When they launched 'A' on 15 June, therefore, the Japanese could call on the ships and aircraft of Ozawa’s 1^st Mobile Fleet from Tawi-Tawi, supported by Vice Admiral Matome Ugaki’s Southern Force from the Batjan islands group near Halmahera in the Molucca Sea, the two forces making rendezvous to the east of the Philippine islands group on 16 June, one day after the US forces landed on Saipan in the Mariana islands group.

Detached from the bulk of the 5^th Fleet, whose amphibious warfare, tactical air support and gunfire support elements were left to operate round the Mariana islands group, the five task groups 3 of TF58 were despatched to the west to guard against any Japanese naval incursion against 'Forager'.

On receiving Redfin's report that the 1^st Mobile Fleet had sortied from Tawi-Tawi on 13 June, Spruance calculated that there was still time to raid the airfields on Iwo Jima and Chichi Jima so as to destroy the 'air bridge' between the Japan home islands and Guam. The attacks were undertaken by Clark’s TG58.1 and Harrill’s TG58.4, which steamed to the north on 14 June, launched their attacks during the afternoon of 15 June and morning of 16 June, and were back with Spruance’s main force by 18 June. The attacks destroyed at least 68 Japanese aircraft at the cost of four US aircraft, and also wrecked several small Japanese freighters.

As the two fleets closed with the Americans heading to the west and the Japanese to the north-east, TF58 3 was disposed in its five major groups: in the van was TG58.7, just to the north of it was the weakest of the carrier groups, TG58.4, and to the east came three groups of four carriers each in a north/south line, namely TG58.1, TG58.2 and TG58.3. This force of large ships had come together on 18 June with the return of TG58.1 and TG58.4 which, as noted, had been detached to make attacks two days earlier on the Japanese installations on Iwo Jima island off to the north.

When the Japanese realised that Saipan was about to be invaded, Ozawa had gathered part of his 1^st Mobile Fleet at Tawi-Tawi, but these forces were already being depleted even before Ozawa sailed from Tawi-Tawi: on 14 May the US submarine Bonefish sank the destroyer Inazuma off Tawi-Tawi, on 5 June the submarine Harder torpedoed and sank the destroyers Minazuki and Hayanami in the same area, and on 8 June Harder then sank the destroyer Tanikaze. Ozawa also suffered bad luck as well as US attack: on 14 June the destroyer Shiratsuyu, evading an imaginary torpedo, collided with the oiler Seiyo Maru, the destroyer losing her stern and having her depth charges detonated. She sank on 15 June with 104 of her men.

Ozawa chose a route through the Philippine islands group, and on leaving the San Bernardino Strait, the 1^st Mobile Fleet was spotted by the submarine Flying Fish during the evening of 15 June. Ozawa’s force then turned to the south-east to link with Ugaki’s Southern Force, which the submarine Seahorse had already spotted, during the evening of 15 June, as its ships steamed to the north-east from Batjan near Halmahera island in the Molucca islands group. The two Japanese forces linked at about 17.00 on 16 June, and at about 12.00 on the following day the fleet refuelled and then shaped a north-easterly course. The submarine Cavalla spotted the second Japanese oiler train early on 17 June, and at 21.15 on the same day, by following the oilers, also spotted the 1^st Mobile Fleet. All the boats had reported their sightings, and in US minds there was now no doubt that the Japanese planned to intervene off the Mariana islands group.

With Cavalla's sighting report in his hands by a time early in the morning of 18 June, Spruance was able to determine his best course of action. As Spruance’s carrier commander, Mitscher recommended a high-speed run straight to the west for a night engagement during the evening of the same day, but Lee, commanding the battleship force, was strongly against any effort to fight a nocturnal engagement for lack of any recent training in night tactics. Spruance also made the controversial decision to remain close to the amphibious forces off Saipan rather than steam toward the advancing Japanese in order to close the range: this decision was influenced by intelligence obtained from Filipino guerrillas, who had captured Japanese plans which discussed the possibility of an end-run by Japanese major surface forces after the main US fleet had been lured away by the Japanese carrier forces. Such a tactic was in fact used by the Japanese, just over three months later, in the 'Battle of Leyte Gulf'.

US aerial reconnaissance just missed spotting Ozawa’s force on 18 June. For reasons which have never been explained, Ozawa received no reconnaissance reports at all from Japanese land-based air forces, but Ozawa’s own scout aircraft sighted TF58 at a time late on 18 June. Obayashi, commanding the 3^rd Carrier Squadron, immediately began to launch an attack, but this was recalled just a few minutes later when Obayashi received Ozawa’s battle plan. This may have been a missed opportunity for the Japanese, as Mitscher was unaware any Japanese carriers were within attack range, and his carriers might therefore have been taken by surprise at dusk.

Further reports reached Spruance during the night of 18/19 June, by which time the US carrier groups were disposed in a north/south line so that each to undertake flight operations without interfering with any other, and the battle line had been formed to their west. A little before 24.00, Spruance received an accurate HF/DF-derived position report that the Japanese forces were 345 miles (555 km) to the west-south-west of the US fleet. Mitscher wished to head to the west in order to attack at dawn, but Spruance was still concerned about the possibility of a Japanese end run against the invasion forces off the Mariana islands group and, after discussing the matter with his staff for an hour, refused. Spruance’s caution was further reinforced by a report that Stingray, patrolling some 300 miles (320 km) to the east-south-east of the HF/DF detection, had sent a garbled and unreadable transmission which Nimitz’s headquarters in the Hawaiian islands group evaluated as having been jammed by the Japanese. Spruance believed that this was a contact report of a much closer Japanese force attempting the very end run he feared, with the HF/DF detection possibly being a deception. Spruance therefore kept his fleet to the east on its designated course, and ordered that TF58 be placed on a purely defensive footing, leaving it to the Japanese to set the pace of the battle. After the battle Spruance came in for much criticism for his decision, but this rightly recognised the paramount importance of shielding the invasion force and therefore depended on the overall superiority of the US carrier arm.

The situation might have been clearer had Spruance received a timely report from a radar-equipped Martin PBM twin-engined flying boat operating from the Saipan area. At 01.15 on 19 June this flying boat detected more than 40 ships in an area some 85 miles (135 km) to the north-east of the HF/DF detection. For reasons never satisfactorily explained, the report did not reach Spruance until after 08.00. Spruance knew fairly accurately how many ships Ozawa had with him, and this report would have accounted for almost all of them, thereby ruling out a Japanese end run in any force. As it was, a night search by radar-equipped Grumman TBF Avenger single-engined carrierborne bombers in the early hours of 19 June turned back just 45 miles (72.5 km) to the east of Ozawa’s van. Meanwhile, Japanese aerial reconnaissance had confirmed the approximate position of the US fleet.

While Spruance knew from his submarines the general position of Ozawa’s fleet, on 18 June his reconnaissance aircraft had located no ships but had spotted Japanese floatplanes involved in their own reconnaissance efforts: it was known that these floatplanes generally operated from cruisers, and their presence indicated that significant Japanese naval forces could not be far distant. Ozawa had to rely largely on land-based aircraft for both reconnaissance and attack, but received no information whatever from Kakuta, although his own aircraft did manage to find most of TF58 as Japanese aircraft had discovered the northern and southern edges of the US task force, some 45 miles (70 km) apart. Ozawa planned to keep out of the range of the US carrierborne aircraft while getting into a position suitable for the launch of his own longer-ranged attack aircraft.

Kakuta had achieved little in his efforts to increase his land-based air strength in the Mariana islands group, partly as a result of adverse weather over the staging bases and partly as a result of the recent US attacks on the Bonin islands group and Iwo Jima. On the morning of 19 June, the Base Air Force's strength at Guam was just 50 aircraft out of the 500 which had been envisaged. Even so, from 05.30, US fighters began to locate and intercept land-based aircraft: over the following 4.5 hours, the US fleet vectored Hellcat fighters against Japanese aircraft over Guam, destroying 30 fighters and five bombers.

Backed by Spruance, Mitscher had opted to deploy his four primary task groups, each with a ring defence, to block any Japanese drive straight through toward Saipan island, but was nevertheless still worried that Ozawa might manage to slip round the northern or southern edges of the US task groups. TG58.2 was placed to the south, 14 miles (22 km) farther to the north was TG58.3, another 14 miles (22 km) farther still to the north was TG58.1, and 14 miles (22 km) directly to the east of this last was TG58.4. Some 17 miles (27 km) to the west of TG58.3 was the Battle Line of TG58.7 in a circle with a picket line of destroyers farther still to the west. To attack the US carriers, therefore, the outnumbered Japanese carrierborne aircraft would have to penetrate the wall of high explosive which TG58.7 would loft, and fight off each carrier group’s combat air patrol and penetrate the anti-aircraft barrage from the escort ships before reaching a position from which to attack the carriers themselves. Notwithstanding Kakuta’s repeated but totally false assertions, the Japanese land-based aircraft had done nothing to reduce the US carriers' strength or to secure Rota and Guam as bastions on which the carrierborne aircraft could refuel and rearm.

Meanwhile, Ozawa prepared for battle. At 06.00 on 18 June, his main force of six carriers set a north-easterly course, effectively reversing to south-south-west at 15.40. At 21.00 Ozawa detached Kurita’s 1^st Mobile Fleet, Mobile Force Vanguard (three light carriers) on an easterly course, while his own group continued to the south until 03.00, turned to the north-east once again, by 04.00 had formed his fleet with the three light carriers of the 3^rd Carrier Squadron and most of his heavy surface units in the van, and the remaining five fleet carriers and one light carrier of the 1^st Carrier Squadron and 2^nd Carrier Squadron about 115 miles (185 km) to the rear. The van formation carried most of Ozawa’s scout floatplanes and, with its heavy anti-aircraft screen, was meant to absorb any US counterattack. However, this left the anti-submarine screen for his rear group dangerously weak. As had been planned, Ozawa intended to launch his attacks from a distance of more than 350 miles (565 km), where his ships would be out of range of any US counterattack.

As noted above, the Japanese plan had started to become apparent to the US naval command in the Pacific after the Japanese rendezvous had been spotted by US patrol submarines, and the scene was thus set for the climactic 'Battle of the Philippine Sea', which is known to the Japanese as the 'Battle of the Marianas' and whose air component was soon to become known to the Americans as the 'Great Marianas Turkey Shoot', on 19/20 June.

During the night of 18/19 June, Spruance began to discern more accurately what was happening away to the west, for his submarines were still accurately reporting the Japanese positions and dispositions, and Ozawa had broken radio silence to order the landplanes based on Guam to attack at dawn, thereby providing the US forces with HF/DF fixes on the position of the Japanese armada, which at 20.23 was 345 miles (555 km) to the west of TF58. Instead of closing the distance, however, Mitscher reversed course as he was still worried that if he steamed too far to the west Ozawa would be able to slip past him. At 06.30 Mitscher ordered TF58 to start zigzagging on a base course roughly south-west by west.

At 04.45 Ozawa ordered the launch of his first group of scout aircraft group, comprising 16 Aichi E13A 'Jake' single-engined floatplanes, from the van force’s battleships and cruisers, and at 07.30 one of these sighted part of the US fleet. A second scout group, this time of one E13A floatplane and 13 Nakajima B5N 'Kate' single-engined carrierborne aircraft, was launched at 05.15 and lost half its number to the US fighter patrol without sighting anything but a few destroyers. Another group of 11 D4Y carrierborne aircraft and two E13A floatplanes, the latter from Mogami, was launched at 0530.

By this time Guam had received a reinforcement of a mere 50 warplanes, rather than the 500 anticipated by Ozawa, warplanes from Truk, Yap and the Palau islands, primarily as Kakuta was not prepared to leave these other fields unprotected against possible diversionary raids. In this desire Kakuta entirely failed to appreciate the larger picture, for 'A' and all that rode on it were dependent on the availability of a force of 500 land-based aircraft on Guam and other island bases. Presumably not wanting to 'lose face', Kakuta still continued to report to Ozawa that Guam was secure and well-stocked with warplanes, fuel, ammunition and other supplies, and that the island’s warplanes were inflicting heavy damage on TF58.

When US radar showed Japanese warplanes approaching Guam on 19 June, Spruance launched a force of his own aircraft to attack Guam first. The island’s airfield came under attack at 07.30, and when the US attackers encountered strong fighter defence, Spruance ordered the launch of more US fighters from Belleau Wood, Cabot, Yorktown and Hornet. At 08.07 radar detected the advent of more Japanese aircraft, also headed toward Guam, but too limited in number to pose any real threat. Believing that Kakuta’s land-based warplanes from Guam, Rota and Yap islands had already struck hard blows at the US ships, Ozawa planned that his attack aircraft would strike their own first blows against the US ships and then land, rearm and refuel on these island bases. In reality the Japanese land-based aircraft had been virtually eliminated by the attentions of the US carrierborne aircraft, and the island airfields were being kept under constant attack. As noted above, Kakuta had seen fit not to report either of these facts to Ozawa.

At 05.30 TF58’s carriers turned north-east into the wind and started to launch their combat air patrols, and at much the same time a number of the 50 or so Japanese aircraft still left on Guam took off on search missions. At 05.50 one of these aircraft found TF58 and, after reporting the position, attacked one of the US destroyers on picket duty and was shot down. Over a period of about 60 minutes the rest of the air strength based on Guam was formed up for an attack on TF58. This wave of attackers was spotted on radar and a group of Grumman F6F Hellcat single-engined fighters from Belleau Wood was sent to investigate. The Hellcat force arrived while the last attack aircraft were still taking off and forming up over Orote airfield. Minutes later additional radar contacts were seen, and these were later discovered to be more aircraft approaching from Saipan and Tinian. A major air engagement followed, 35 of the Japanese aircraft being shot down, and the battle was still going an hour later when the Hellcat fighters were recalled to their carriers after the discovery of Japanese aircraft approaching TF58 from the west.

Ozawa had ordered the launch, at 08.30, of the first Japanese carrierborne attack force. This comprised 16 Mitsubishi A6M Reisen 'Zero' single-engined air combat fighters, 45 A6M bomb-carrying fighters and eight B6N torpedo bombers from the carriers of the 3^rd Carrier Division, and these aircraft were discovered by the radar of the Battle Line’s ships at 10.00 at a range of 175 miles (280 km). At 10.10 Mitscher recalled the fighters operating over Guam and at 10.19 ordered every fighter on this carriers into the air to meet the attack. The carrier of all the groups turned into the wind and launched their aircraft between 10.23 and 10.38, at which time the Japanese aircraft were 85 miles (140 km) away. The Japanese attackers paused to regroup at about this time, giving the US fighters to reach an altitude suitable for their interception of the Japanese attack force, and granting the Americans the time they needed to fly off all their attack aircraft. The clearing of the carriers' flightdecks made it possible for the carriers to undertake a continuous cycle of fighter operations.

The air battle which now took place clearly displayed the improvements which had been effected in US carrierborne fighter, carrier battle tactical formation, fighter director and pilot capabilities, and as the reverse of this tactical coin highlighted the lack of capability which characterised the new, poorly trained Japanese pilots flying aircraft which were obsolescent by comparison with those of the US Navy.

The Japanese pilots had committed a disastrous error in deciding to circle and regroup their formations for the attack, for the resulting 10-minute delay allowed the first group of Hellcat fighters to meet and engage the attacking force at 10.36. These first Hellcat fighters were quickly joined by additional groups, and within minutes 25 Japanese aircraft had been shot down for the loss of only one US fighter. The Japanese attackers who survived this initial interception were now met by other fighters, and lost another 16 of their number. Some of the surviving aircraft attacked the radar picket destroyers Yarnall and Stockham, but caused no damage. Three or four bombers broke through to the battleship group, and one made a direct hit on South Dakota, causing many casualties (including 27 men killed) but not otherwise discommoding the battleship. None of the aircraft launched in Ozawa’s first attack got through to tackle TF58’s carriers, and 42 of them were lost to the American fighters and anti-aircraft fire. Working with the carrierborne fighters, the ships of the Battle Line had effectively devastated the raid.

Ozawa’s second attack was launched from the Main Body (the three fleet carriers of Force 'A' and three light carriers of Force 'B') at 08.56, and was the largest of the day as it involved 53 D4Y dive-bombers, 27 B6N torpedo bombers and 48 A6M fighters. The aircraft made the mistake of flying over the Japanese van group and lost two aircraft to 'friendly fire', while another eight were damaged and forced to return to their carriers. At 11.07 US radar detected the aircraft of this second attack at a range of 130 miles (210 km), and they were intercepted while still 60 miles (100 km) out from their target ships: no less than 70 of them were shot down before the Japanese force reached the ships. The surviving Japanese aircraft wasted much of their firepower in unsuccessful attacks on the picket destroyer Stockham, then attacked Lee’s Battle Line: the torpedo of one B6N struck Indiana on the waterline, but failed to explode. Six aircraft attacked TG58.2, scoring near misses which caused casualties on two of the carriers, and four of these aircraft were shot down. A small group of torpedo bombers attacked Enterprise, launching a torpedo which exploded in the carrier’s wake. Three other torpedo bombers attacked the light carrier Princeton, but were shot down. In all, 108 of the 110 aircraft in the second Japanese attack were downed, so just two of the aircraft reached Guam and Rota.

Ozawa nonetheless persevered, for despite the losses of his own force he still felt no reason to disbelieve Kakuta’s false reports that TF58 was being hard hit by land-based aircraft. At 10.00, therefore, Ozawa launched his third attack force, comprising 15 A6M combat fighters, 25 A6M bomb-armed fighters and seven B6N torpedo bombers from the carriers of the 2^nd Carrier Squadron. This group was directed too far to the north as a result of a garbled report from the third scout group. Most of the aircraft returned to their carriers, but about 20 received a corrected sighting report and turned to the south, avoiding the Battle Line and attacking TG58.1. The Japanese aircraft were detected at a range of 110 miles (175 km) and intercepted at 13.00 at a distance of 55 miles (90 km) by 40 Hellcat fighters, which shot down seven Japanese aircraft, but a few aircraft managed to break through and launch an ineffective attack on the Enterprise group. Many of the other Japanese aircraft did not press home their attacks, so this third attack wave suffered proportionally fewer casualties than the first and second waves, and 40 of the aircraft managed to return to their carriers.

At this point there was a brief lull in the battle, during which Mitscher despatched a scout mission which failed to find the Japanese fleet.

A strong fourth attack was launched from the carriers of the 1^st Carrier Squadron and 2^nd Carrier Squadron between 11.00 and 11.30, and took the form of 30 A6M air combat fighters, 10 A6M bomb-armed fighters, nine D4Y and 27 D3A dive-bombers and six B6N torpedo bombers, and these too were acutely misdirected as a result of garbled reports from the third scout mission and therefore initially failed to find TF58. The aircraft then broke into two loose groups and turned toward Guam and Rota in the hope of refuelling. One group of aircraft flying toward Rota chanced on TG58.2, 18 of them joining combat with the US fighters and losing half their number. Another group heading for Guam included nine dive-bombers which evaded the US fighter defence and attacked Wasp and Bunker Hill, but failed to make any hits, losing eight of their number in the process. The larger group of Japanese aircraft had flown toward Guam and had jettisoned its ordnance in preparation for landing when it was intercepted over Orote by 27 Hellcat fighters from Cowpens, Essex and Hornet: 30 of these 49 aircraft were shot down, and the rest were damaged beyond repair when examined after landing.

Thus the fourth Japanese attack had lost 73 of its 82 aircraft either shot down or irreparably damaged.

The large numbers of Hellcat fighters which intercepted the four Japanese attacks had benefited greatly from the expert control they received from the combat information centres which now constituted the operational hearts of the US carriers. The fighters were also aided by the perfect weather conditions, which provided clear skies, unlimited visibility, and the humidity conditions which caused the Japanese warplanes to leave tell-tale vapour trails in their wakes. Finally, the Japanese aircraft which did mange to break through the US fighter patrols then had to face the dense barrage of anti-aircraft fire lofted by the US warships: the single most important weapon in the US ships' anti-aircraft armoury was the superb 5-in (127-mm) dual-purpose gun carried by battleships, carriers, cruisers and destroyers and provided with fire control by the Mk 37 director.

Even as the US fighters were destroying the Japanese carrierborne aircraft attempting to reach and sink the US carriers, Spruance had ordered attacks on Guam. At 10.40 Hornet launched 17 SB2C and seven TBF attack aircraft, escorted by 12 F6F fighters, to bomb Orote airfield, which was attacked once again at 13.00 by a group of SBD dive-bombers which had been circling for two hours after being launched from Lexington primarily to clear the carrier’s flightdeck for fighter operations. Other US attack aircraft launched under similar circumstances continued to attack throughout the day. For all practical purposes, Orote airfield was destroyed, and many of the aircraft of the Japanese fourth raid which had to be written off after landing had in fact crashed on the bombed-out runway. But this came at a heavy cost: the Japanese anti-aircraft fire over Orote was reportedly the worst yet encountered in the Pacific war, and the Americans lost seven aircraft over the airfield.

At 08.16 the submarine Albacore had sighted the carrier group commanded by Ozawa. The target which could be approached and attacked most readily was Taiho, only recently completed and serving as Ozawa’s flagship. As Albacore was about to fire, the submarine’s fire-control computer failed and at 09.10 the torpedoes were fired by eye at Taiho, which had just launched 42 aircraft as a part of the second attack wave. Four of the submarine’s spread of six torpedoes were off-target. The pilot of one just-launched aeroplane sighted one of the two which were heading for Taiho and crashed his aeroplane onto it, but the other struck the carrier on the starboard side near her aviation fuel tanks, causing damage which did not initially appear to be very serious, even though the forward elevator was rendered inoperable.

Another US submarine, Cavalla, was able by about 12.00 to reach a position from which to engage Shokaku. Three torpedoes hit the carrier, setting her on fire. At 15.00 the fire reached the bomb magazine, and Shokaku was blown apart in the resulting explosion.

Meanwhile Taiho was succumbing to the effects of inadequate damage control and the captain’s poor judgement in maintaining a speed of 26 kt: on the instruction of an inexperienced damage-control officer, the carrier’s ventilation system had been operated at maximum capacity in an attempt to clear explosive fumes from the ship, but all this had achieved was the spreading of a highly volatile fuel/air vapour right through the carrier. At 15.30 an explosion tore through the ship, the fires now burning to fiercely that other ships could not close her to help fight the fires or rescue the crew. The carrier finally sank at 17.28, and of her crew of 2,150 some 1,650 were lost.

The ships of TF58 had steamed to the west during the night in order to attack the Japanese at dawn, and scout aircraft were launched at first light. Ozawa had meanwhile transferred to the destroyer Wakatsuki after Taiho had been hit, but the destroyer’s radio equipment was not capable of sending the number of messages needed, so the Japanese commander had transferred again, first to the heavy cruiser Haguro and then at 13.00 to Zuikaku which, since the sinking of Shokaku, had become the only survivor of the six fleet carriers which had undertaken the 'Ai' attack on Pearl Harbor in December 1941. It was only on boarding the carrier that Ozawa finally learned of the previous day’s disastrous missions, and that the Japanese carrier force now had only 102 aircraft left.

Up to the end of the fourth Japanese air attack, TF58 had been concerned only with protecting its own ships as it was out of aircraft range of the Japanese force and its carriers had made no effort to launch any US force of attack aircraft. By this time. though, Spruance had come to the conclusion that a Japanese end run against the amphibious forces off Saipan was very unlikely and that the time had now arrived for TF58 to start to take the war to the 1^st Mobile Force.

Shortly after the sinking of Taiho, the 1^st Mobile Fleet started to pull back, the Main Body Force 'A' and Main Body Force 'B' steaming to the north-west with the 1^st Mobile Fleet, Mobile Force Vanguard following it. But Ozawa had still not admitted defeat, for even though he had only few aircraft left, reports from his own crews combined with those from Kakuta to indicate that that several US carriers had been sunk. Kakuta had also sent a radio message to Ozawa telling him that many of his aircraft had or were still landing on Guam. Additionally, Ozawa still believed that Kakuta was calling in hundreds of additional warplanes with which to continue the attack on TF58.

At this time Ozawa believed that he was still in the fight. Mitscher had undertaken no night search, and TF58 was making 24 kt to the north-west as Ozawa’s force was managing only 18 kt. A night sighting and a morning attack by Mitscher might well have inflicted still more serious damage on the 1^st Mobile Fleet, but Mitscher did not know the location of Ozawa’s remaining ships, and did not find out until 15.40 on the following day. Ozawa began to refuel in the afternoon, but at 16.15 the heavy cruiser Atago reported, by interpreting a radio call to Mitscher, that TF58 had discovered the location of the Japanese force. Ozawa immediately halted the refuelling operation and, increasing to 24 kt, headed to the north-west.

At 15.00 on June 19 Spruance authorised Mitscher to pursue Ozawa’s fleet. Mitscher left Harrill’s TG58.4, whose ships were now short of fuel, to continue interdicting the airfields on Guam and Rota, as pursued the Japanese with his three other carrier groups. As they were recovering aircraft, these were unable to head to the west until 20.00, and Mitscher dared to steam at no more than 23 kt in order to conserve fuel. However, Ozawa was unaware of the extent of his aircraft losses on 19 June, in the belief that most of his aircraft had landed safely on Guam, and was therefore slow to break away and thereby open the range to be covered by the large numbers of warplanes he expected to return to the carriers. As a result, the Japanese fleet was finally located by US search aircraft at 15.40 on 20 June.

Mitscher now faced a difficult decision. The 15.40 report had been so garbled that the US admiral did not know what had been sighted or its precise location. At 16.05 another report helped to clarify the situation, however, and it was at this stage that Mitscher was faced with having to decide whether or not to launch a full strike even though there were only 75 minutes to sunset. To make the attack on the Japanese ships, the US pilots would have to fly to extreme range and then return to their carriers at night, and Mitscher appreciated that many of the pilots might not make it back to the carriers. Nevertheless, at 16.20 he ordered the all-out attack, and by 16.36 some 85 fighters, 77 dive-bombers and 54 torpedo bombers had lifted off from six fleet and five light carriers.

At this time the Japanese force was divided into three groups. The first group comprised the fleet carrier Zuikaku and heavy cruisers Haguro and Myoko, screened by destroyers. Some 22 miles (35 km) to the south-west of this a second group comprised the light carriers Junyo, Hiyo and Ryuho, battleship Nagato and heavy cruiser Mogami, screened by destroyers. Some 11.5 miles (18.5 km) to the south the third group comprised the light carriers Chitose, Chiyoda and Zuiho, super-battleships Musashi and Yamato, battleships Kongo and Haruna, and heavy cruisers Takao, Maya, Atago, Kumano, Suzuya, Tone and Chikuma, screened once again by destroyers. Also involved in the Japanese movement were the oilers, accompanied by more destroyers.

Ozawa could launch only about 75 aircraft before TF58’s force of 216 warplanes arrived overhead just as the sun was setting. In the raid, which lasted from 18.40 to 19.00, Hiyo was hit at least once and possibly twice by torpedoes from four of Belleau Wood's TBF attack aircraft, suffered a major internal explosion, caught fire and sank at 20.32 taking about 250 men with her and leave another 1,000 to be rescued by destroyers. Wasp's aircraft were so short of fuel that they attacked the first Japanese ships they spotted, which were the oilers of the support force, and immediately attacked them. Three of the oilers were hit and severely damaged: Genyo Maru and Seiyo Maru were later scuttled, but the third managed to extinguish her fire and get under way once more. Extensive damage was suffered by the fleet carriers Zuikaku and Junyo, the light carrier Chiyoda, and the heavy cruiser Maya. The destroyer Shigure was hit by a small bomb, while the battleship Haruna suffered one direct hit aft, two on her quarterdeck which penetrated two lower decks causing flooding and heavy topside damage, and two near misses on her port bow which bent the hull and killed 15 men.

The US losses in this attack amounted to 20 aircraft, and it was only in the darkness at 20.45 that the first US aircraft began to return to TF58’s carriers. Mitscher took the difficult decision to illuminate his carriers fully with running lights, deck lights and searchlights despite the risk that these would attract attacks from submarines and night-flying aircraft, and the picket destroyers fired star shells to help the returning aircraft to find the US task groups. Despite this effort, 80 of the returning aircraft were lost, some crashing on flightdecks but the majority coming down onto the sea. Many of the crews were rescued over the next few days, however, and the US aircrew losses were therefore only 49 men.

It was not just the Americans who suffered from night landings, though, for Ozawa’s fighters did not begin landing until 19.30 on 20 June, many of ditching into the sea crashing on damaged flightdecks. The result was that Ozawa now possessed a mere 35 operational aircraft. Ozawa’s half-hearted attempt to plan and seek a surface engagement, which was ordered at 19.00, was cancelled at 22.05.

During the night Ozawa received orders from Toyoda, commander-in-chief of the Combined Fleet, to withdraw from the Philippine Sea. None of Ozawa’s remaining ships had suffered damage to their machinery, so Ozawa’s force was able to maintain a speed of 20 kt, ensuring his escape. Spruance nevertheless pursued until a time late on 21 June in the hope of catching and overwhelming any crippled vessels, but there were none, and Spruance called off the chase at 20.30, thereby ending the 'Battle of the Philippine Sea'.

The four Japanese attacks had used 373 carrierborne aircraft, of which a mere 130 returned to the carriers, and several more were destroyed on board the two carriers lost on the battle’s first day. After the second day the Japanese total losses were three fleet carriers, 395 carrierborne aircraft and two oilers, and other ships had been severely damaged; the total Japanese air losses, including land-based machines, were between 550 and 645 aircraft.

The losses on the US side on the first day were just 23 aircraft, and on the second 100, most of the latter in night landings; the Americans lost no ships, and in fact sustained damage to just one battleship.

The Japanese 'decisive battle' had again been lost, but Ozawa cannot be faulted for his part in it. He had been ordered into battle with a force half the size of that at the disposal of his opponent and with obsolescent aircraft manned by inadequately trained aircrew. Ozawa fully expected, but did not get, the support of Kakuta’s 250 or more land-based aircraft, which might have made the battle more even. His greatest error was in allowing his inexperienced air crews to tackle the heavily gunned Battle Line, a new US tactical formation specially designed to draw away and decimate aircraft which might otherwise attack the more vulnerable but considerably more valuable aircraft carriers. Ozawa was misled in the direction of his third and fourth attacks in the matter of TF58’s location, and was led to believe that Guam was a sanctuary rather than the death trap that it actually was. Even if everything had gone right, however, it would have been truly extraordinary if Ozawa could have gained the upper hand over the US Navy’s larger numbers of carriers and more modern aircraft, and its new tactic of a battle line bristling with huge firepower. At best, some of the US carriers might have been damaged or sunk, but thus would not have been a strategic disaster as many more were already on their way to completion and service.

The Japanese losses were wholly irreplaceable, so in the Battle of Leyte Gulf, resulting from their 'Sho' operation a few months later, the Japanese carriers were used solely as decoys as there were neither aircraft nor crews with which to re-equip them. 'A' and the consequent Battle of the Philippine Sea thus marked the end of the Japanese navy’s air arm as an effective weapon.

Spruance’s battle plan was conservative, but while it did not result in the destruction of all the Japanese aircraft carriers, it did succeeded in so severely weakening the Japanese carrierborne air arm, by killing most of the trained pilots left to it and by destroying their last operational reserves of naval aircraft, that it was left effectively impotent. Without the time or resources needed to build sufficient aircraft and to train pilots to the level of useful experience, the surviving Japanese carriers were useless as weapons, a fact acknowledged by the Japanese themselves and they deployed them as sacrificial decoys in the 'Battle of Leyte Gulf' four months later. With its best offensive arm effectively crippled, Japan was increasingly forced to rely on land-based kamikaze aircraft in a last-ditch effort to make the war so costly that the US would offer peace terms rather than demand unconditional surrender.

Spruance came under strong criticism after the battle by many officers, particularly those of the air arm, for his decision to fight the battle cautiously rather than attempting a more aggressive exploitation of his greater strength and better intelligence information. The critics argued that, by not closing of the Japanese earlier and more dynamically, he wasted the opportunity to destroy the 1^st Mobile Fleet. Among the severest of Spruance’s critics was Vice Admiral John H. Towers, a naval aviation pioneer and deputy commander-in-chief of the Pacific Fleet, who demanded that Spruance be relieved: this demand was rejected by the more perspicacious Nimitz who, with Turner, the commander of the 5^th Amphibious Force, and Admiral Ernest J. King, the commander of the US Fleet and Chief of Naval Operations, fully approved Spruance’s handling of the battle.

It is instructive to compare Spruance’s caution (and in particular his suspicion of a Japanese use of diversionary force to open the way for an end-run attack on the US amphibious forces) with the lack of this same quality displayed by Halsey, commander-in-chief of the 3^rd Fleet, in his headlong pursuit of a real Japanese diversionary force in the Battle of Leyte Gulf. In this latter battle, Halsey’s decision to pursue Ozawa’s now-toothless carrier force left the US invasion fleet, containing vulnerable transports filled with tens of thousands of troops, to be screened off Leyte island by only escort carriers and destroyers. These had the primary task of anti-submarine patrol and support of the landed troops, but were left wholly exposed to an attack by a fleet of heavy Japanese surface units during the 'Battle off Samar'. Halsey’s headlong pursuit to catch and destroy a toothless opponent thus created a crisis in which the Americans narrowly averted a strategic disaster.

Although the US carrierborne aircraft attacks destroyed fewer Japanese ships than they had in earlier battles, US submarines compensated for this by sinking two of the three Japanese fleet carriers. And most importantly of all, the air defence of TF58 had shattered the Japanese naval air arm in a blow from which it never recovered. In this the F6F fighter proved decisive as it combined a powerful engine for superior performance, a rugged airframe, good protection and adequate firepower made it an excellent warplane. By comparison, the Japanese were still flying the A6M which, while highly agile and a superb dogfighter during the early stages of the Pacific War, was now showing the age of its basic design as by a time as early as 1943 it was clearly underpowered and structurally fragile. Added to the limitations of almost all of its aircraft, including some which were more modern than the A6M, the Japanese naval air arm had by the middle of 1944 come to suffer the failures of its training programmes. Believing in 1941 that the war would be won swiftly, the Japanese navy had decided that it task could be accomplished by the forces already on hand and had already started to reduce its training efforts. By the beginning of 1944, therefore, the Japanese naval air arm could not replace the last survivors of the highly trained aircrews with which it had entered the war in December 1941. The Americans lost fewer than 25 F6F fighters in air-to-air combat, and gained nearly 480 'kills', 346 of those being of carrierborne aircraft on 19 June in the 'Great Marianas Turkey Shoot'.