Battle of the Philippine Sea   19 - 20 June 1944
The Great Marianas Turkey Shoot
The Last Carrier Battle

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The Battle of the Philippine Sea was fought as the Imperial Japanese Navy attempted to repel the USN capture of the Marianas -- Saipan, Tinian, Guam. It was the final carrier battle of WW2 and probably of all time. The Japanese counterattack included nine carriers and was defeated, although most of the fleet escaped.
The Big Picture.
The Americans were in the Central Pacific to take the island of Saipan to break the line of defenses Japan had built. Saipan was within B-29 range of Tokyo and the destruction of Japanese industry would be able to begin. The Americans knew the Japanese had to defend this line in a all out battle, thus there would be a fight and with it the opportunity to destroy the new Japanese fleet.
Japan had longer range air search capability than the US. They also had longer ranged attack aircraft. This was the key to the Japanese plan was to find the US fleet before their opponents and keep the Japanese fleet out of range of the Americans, then to attack without the Americans being able to respond.
Background.
The Japanese plan for the war was to remove the fleets of all other nations from the Pacific and take the natural resources of the East Indies that were needed to complete their conquest of China. It was expected that they could then make peace and retain their conquests. This led to little long range planning of military design or training.
    Fletcher had stopped the Japanese advance in the first three carrier battles of the Pacific War - saving Australia at Coral Sea, saving Hawaii at Midway, and Guadalcanal at Eastern Solomons. The Japanese carrier fleet was further weakened in the fourth carrier battle at Santa Cruz and the surface fleet battles at Guadalcanal. Then both sides withdrew to rebuild their fleets. In 1943 Japan commissioned 13 carriers in new construction or by conversion of other ships to aircraft carriers while the US commissioned 15 carriers and 37 escorts (used as aircraft ferries and for anti-submarine patrol.)
    Training to replace pilots was in full swing in the United States who was turning out ??? new pilots a year starting before pearl Harbor.
    US industry mobilized, and as soon as the Navy had enough ships and trained troops, they started a march across the central Pacific starting with the Gilberts campaign (Tarawa, Makin) in 21Nov 1943, then the Marshalls (Kwajalein, Enewetok) 31 January 1944, and now it was the Marianas. The Marines had learned how to land on defended islands.
B-29 was a "very heavy bomber" with a 3,??? mile range of operations. From bases in China, the first squadron attacked the southern, military island of Kayshu. However, every bomb, every gallon of fuel, every bit of supplies had to be shipped through the south Atlantic, round the tip of Africa and across the Indian Ocean to Indian, then by railroad to northern India where flown over the Himilaya Mountains, "The Hump", into SW China. It was a logistic nightmare. From the Marianas, the B-29 could reach Tokyo and industrial heartland of Japan. Once airbases could be readied there, the China squadrons would relocate to take advantage of shorter supply lines and greater area of open to attack.
Training. The IJN started the war with a group of combat pilots trained in the ongoing war in China and with equally suitable aircraft with the Zero fighter unquestionably the best sea-level fighter in the world. The Japanese war goals were achieved in only five months and no thought was given to further development and training. But in war, pilots are lost. Fletcher's task forces and Army aircraft caused the Japanese to lose planes and most of the experienced pilots and aircrews at an increasing rate. Entire squadrons were decimated and the survivors assigned to train new pilots. The Zero was never replaced during the war, whereas the Americans introduced several new high-performance aircraft including the workhorse Hellcat fighter that outperformed the Zero at all altitudes. Japan had not the fuel to allow extensive flight training, the Americans were superbly trained.
Preliminaries
Aircraft from 15 US carriers overwhelmed the airfields of the Marianas beginning 11 June. The American fleet put itself between the marine landing and the Japanese fleet while support destruction of strong points during the landings. To protect their flank they sent two task forces to attack the airfields of Iwo Jima, 700 miles to the north. The weather was bad, so that many aircraft were destroyed on the ground. Craters put in airfields were quickly repaired but planes could not land as quickly on the damaged fields.
Submarines interdicted Japanese supply convoys to the Marianas, for example, five of seven ships carrying half of 34th Division were sunk. Many troops were rescued, but their equipment was lost.
The Japanese had moved the fleet from the home islands to the south to be near a source of fuel. When the airstikes began at Saipan, Adm. Ozawa quickly assembled his forces from Borneo, Mindanao, and Halmanera to move into the Philippine Sea towards the Marianas. The plan was to coordinate attacks by 400 carrier and 500 land based aircraft on the US fleet. Long range scouts soon found the US fleet to their peril, most were detected by radar and destroyed. American scouts could not reach the location of the Japanese fleet, but Japanese units were spotted June 13 as they passed through submarine scouting lines. The subs would surface at night and radio the details of the sightings that day.
The reports made Adm Spruance believe the Japanese had split their forces. Fearing an end run, he had returned towards Saipan overnight before the Japanese attack. The invasion of Guam, scheduled for 18 June, was postponed for over a month. However, Albacore followed and torpedoed Ozawa's flagship, Taiho, which continued launching. Fumes ignitied later that afternoon ; about the same time Cavalla put four torpedoes into Skokaku.
Japanese Attack. The Japanese carriers launched all their aircraft in four waves, one each hour. The spirited Japanese pilots were detected by radar and while the inexperienced Japanese squadrons took time to form up, the Americans climbed to altitude and position to intercept. Wave One had 64 aircraft, 42 failed to return. Wave Two had 119 planes of which 97 went down. Wave Three's orders were changed in flight and not everybody got the word, half simply returned; seven others never returned. Wave four of 82 aircraft got lost from a bad scouting report and most diverted to Guam and were intercepted with wheels down, none flew again. The other half heading for Rota found a task force and made an ineffective attack losing 14 planes.
The wind favored the Japanese, they could launch into the wind, whereas the Americans had to reverse course to launch and to recover aircraft. The Japanese could pick their attack, the Americans could make little progress to close with the Japanese during flight operation, in fact was forced back to within sight of Rota and Guam.
    Adm Ozawa was not aware of his loss of 445 pilots and air crew because the flights were authorized to land at airfields to rearm and attack again before returning to their carriers. He turned he Japanese fleet north to refuel and be ready to attack again when the shuttle aircraft returned.
American Attack.     After dark, the US Task Forces headed for the previous Japanese position. The Japanese carriers and oilers were not found until 4 p.m. the next day. Only then did Spruance feel secure enough that he would consider an attack on the vulnerable Japanese fleet. The Japanese fleet were beyond attack range, yet the decision was reached to go ahead even tho the 216 planes would be landing after dark with empty fuel tanks.
    The attack was marginally successful. One carrier,Hiyo, and two oilers were sunk and the rest got away, but with 35 aircraft remaining of the original 430 ; the Japanese carriers never entered combat again and the empty carriers were sacrificed as decoys in the Battle off Cape Engano, 25 Oct 1944.
    The returning Navy aircraft, low on fuel, started landing in the sea, some by divisions with hopes of a greater chance of rescue. Extreme measures were taken to save the returning planes. The fleet was lighted, risking submarine detection, and some landed planes were pushed over the side to make room for others flying on fumes. 80 planes landed in the sea; ?? pilots and aircrew were lost.
    Three weeks of intensive combat were required to secure Saipan on July 9, then Guam and Tinian were taken. Sea Bees prepared the island for aircraft. On the 12th, P-47 fighters flew from Saipan against resistance on Guam. By Aug 4th, B-25 medium bombers staged through Saipan to help finish retaking Guam. Tinian became the busiest site were eight long runways were built. B-24 heavy bombers suppressed islands in the north central Pacific. The first B-29 strike was from Tinian with an 81 bomber raid on Tokyo on Nov 24. Raids built up to 600 planes launched every few days such that all stragegic targets had been hit twice by war-end ; the largest raid was 784 B-29 bombers 1 Aug'45. Afterward

Appendix

Mariana Islands are comprised of Guam and a chain of 15 islands running north that include Saipan, Tinian and Rota. These islands had been settled for thousands of years before discovered by Megellen and colonized by Spain as a rest stop between the Philippines and Mexico. The US took over Guam during the Spanish American war along with the Philippines, and Wake Island. Guam was used by the US as a naval transit station.
The Northern Marianas 15 islands are considered a separate organization. All together they make up 180 sq. miles (477sqKm). After the Spanish American war the northern Marianas were sold to Germany. Japan received the islands as a League of Nations mandate for her participation in WWI on the side of the Allies. Although pledged to remain unfortified, Japanese troops from Saipan captured Guam two days after Pearl Harbor.
Saipan is the second largest island. Located about 120 miles (200 km) north of Guam, Saipan is about 12.5 miles long (20 km) and 5.5 miles wide (5.5 mi) with a total area of 46.5 sq miles (120 kmē) Japan made this their headquarters and the most heavily defended of the islands. U.S. marines landed 15 June 1944, and fought for three weeks to secure the island.
Guam is the largest and southernmost island of the Marianas. Guam is 32 miles long, from 3 to 10 miles broad, and about 200 sq. miles (520 sqKm) in area and possessing a good harbor. Guam was used by the US as a naval station with no weapons larger than .30 cal machine gun.. Japan captured Guam on Dec 10, 1941, after a twenty minute defense. US troops landed July 21, 1944, and secured the island August 10.
Tinian Tinian is about 5 miles (8km) southwest of Saipan. It has a land area of about 40 sq.mi. (100 kmē). Marines landed there 24 July 1944 and fought until a final Japanese suicide charge on 31July 1944. Tinian became the busiest air base in the islands with eight runways for B-29's. Bombing of mainland Japan began 24 Nov 44 from Tinian.
Rota is 47 miles north of Guam and 63 miles south of Tinian and is 10.5 miles long, 3 miles wide and contains 33 square miles. Rota was bypassed and not occupied until after the war.
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