[11] Koga's chief of staff, Vice Admiral Shigeru Fukudome, was flying in an accompanying plane and carrying the Z Plan documents, and also crashed.

Fukudome survived, but the Z Plan briefcase did not sink with the destroyed aircraft and was recovered by Filipino guerillas who over the next few weeks transported the documents to General Douglas MacArthur's Military Intelligence Service (MIS) in Brisbane, Australia.

[10] Japan no longer had enough oil tankers to transport the required volume of petroleum from the Dutch East Indies to Japanese refineries.

Without adequate supplies of refined residual fuel oil, Japanese aircraft carriers refueled with unrefined Tarakan petroleum in June 1944.

Since control of the Marianas would bring American strategic bombers within range of the Japanese home islands, the IJN decided it was time for the long-awaited Kantai Kessen (decisive battle).

In addition to extensive command facilities, reinforced torpedo blisters and a large air group, Taihō was the first Japanese carrier with an armor-plated flight deck, designed to withstand bomb hits with minimal damage.

At 18:35 on 15 June the submarine USS Flying Fish sighted a Japanese carrier and battleship force coming out of San Bernardino Strait.

[19] TF 52's battleships, cruisers and escort carrier groups were ordered to remain near Saipan to protect the invasion fleet and provide air support for the landings.

Shortly after learning Lee's opinion, Mitscher requested permission from Spruance to move TF 58 west during the night, to reach a launch position at dawn that would allow for a maximum aerial assault on the enemy force.

"[24] Spruance's decision was influenced by his orders from Nimitz, who had made it clear that the protection of the invasion fleet was the primary mission of TF 58.

[23] Spruance's decision in this matter, although subsequently criticized, was certainly justified; by this point in the war, it was well known that Japanese operational plans frequently relied on the use of decoys and diversionary forces.

[27] The U.S. Navy had developed a sophisticated air control system, which vectored CAP fighters by radar to intercept enemy bombers well before they reached the fleet.

Between three and six bombers broke through to Lee's battleship group and attacked; one bomb hit the main deck of USS South Dakota, killing or injuring over 50 men but failing to disable her.

A smaller group of nine Japanese dive bombers of this force evaded U.S. aircraft and attacked Wasp and Bunker Hill but scored no hits; eight were shot down.

Taihō quickly resumed regular operations, but gasoline vapor from the ruptured fuel tanks began to fill the hangar decks, creating an increasingly dangerous situation on board.

One torpedo had hit the forward aviation fuel tanks near the main hangar, and aircraft that had just landed and were being refueled exploded into flames.

At approximately 14:30, a spark from an electric generator on the hangar deck ignited the accumulated fumes, triggering a series of catastrophic explosions.

The strike group from Wasp, more concerned with their low fuel levels than with finding the more important Japanese carriers and battleships, dived on the tankers.

[43][page needed] After the protracted strike, it became clear that most of the aircraft returning to their carriers were running dangerously low on fuel, and to worsen matters, night had fallen.

Some pilots intentionally went down in groups to facilitate rescue, and more ditched individually either in a controlled landing with a few gallons of fuel left or in a crash after their engines ran dry.

[45][page needed] Approximately three-quarters of the crews were rescued from the sea, either that night from crash locations within the task forces, or over the next few days for those further out, as search planes and destroyers criss-crossed the ocean looking for them.

The aircraft and trained pilots lost at Philippine Sea were an irreplaceable blow to the already outnumbered Japanese fleet air arm.

With the effective crippling of her best striking arm, Japan chose to rely increasingly on land-based kamikaze suicide aircraft in a last-ditch effort to make the war so costly that the U.S. would offer peace terms better than unconditional surrender.

By failing to close on the enemy earlier and more forcefully, his critics argue, he squandered an opportunity to destroy the entire Japanese Mobile Fleet.

Halsey left the American invasion fleet weakly protected during the Battle off Samar, nearly resulting in a devastating attack on the landing force by Japanese heavy surface units.

It was prevented only by the heroic and desperate attack of 5 small American surface ships, which put up such an intense fight that the 23-ship-strong Japanese fleet thought they were engaging a much larger force and withdrew.

Likewise, during the carrier-based air raids, U.S. carriers were in a vulnerable position, and the low visibility coupled with radar confusion let a Japanese bomber slip through and severely damage USS Franklin.

The American F6F Hellcat fighter proved its worth, as its powerful engine generated superior speed, while its heavier armor and firepower made it rugged and deadly.

The Japanese on the other hand were still flying the A6M Zero which, though highly maneuverable and revolutionary during the early stages of the Pacific War, was now underpowered, fragile and essentially obsolete by 1944.

On that very same day Yamato and Musashi and their supporting ships received new orders to head north to screen aircraft carriers that were about to begin Operation A-Go.