The Pacific War began in 1941, after Japanese aircraft bombed the American Pacific fleet stationed at Pearl Harbor. This fleet was largely destroyed, as Imperial Japanese Navy planes wiped out five battleships during the raid. In addition to this, America lost hundreds of aircraft at airfields. Japan declared war on the USA.
In early 1942, Japan was rampant in the war. The empire's objective was to gain territory in the Pacific region that would provide raw materials and supplies. To this end, territory under European dominion were largely the targets. Overall, Japan was able to defeat a number of European and U.S. armies as Singapore, the Dutch East Indies and the Philippines all fell.
The Allies retreated from these regions, but were not defeated. Despite Pearl Harbor, the American navy had the potential to expand, and perhaps more importantly four U.S. aircraft were not present during the raid. Consequently, the American carriers remained the Allies most potent strategic threat to the Japanese Empire.
The first naval battle of the Pacific War happened at Coral Sea in 1942. The Imperial Japanese Navy was targeting Port Moresby to first cut the American supply line with Australia, and then secondly to put Australia within range of bombers. To defend Port Moresby, the U.S. Navy made good use of its carriers that intercepted the IJN fleet at Coral Sea. This was the first naval battle to involve aircraft carriers. While it was an indecisive encounter, the IJN retreated from Port Moresby.
This set back prompted the IJN to target Midway as a way of trapping the American aircraft carriers. Admiral Nimitz was well aware of the Japanese fleet heading for Midway thanks to Allied code breaking. At the Battle of Midway, American bombers bombed four Japanese aircraft carriers, which sank along with hundreds of aircraft. The Japanese were left little option but to retreat from Midway, and the Battle of Midway was the first notable naval defeat for the IJN.
In 1944, the Allies were making a steady advance in the Pacific. The Marianas became the next target for the United States, which would then provide a clear route towards the Philippines, which would cut off Japan's oil supplies. Saipan was the next point of the Allied advance towards the Philippines.
The IJN mobilized its aircraft carriers to prevent an American landing at Saipan. These aircraft carriers would be split into three forces: A, B and C. The A Force was the largest of these with about 400 to 500 aircraft.
But the Japanese plan started to fall apart before the battle had begun. Shortly before the battle U.S. aircraft blitzed Japanese airfields in the Marianas. U.S. aircraft destroyed hundreds of Japanese aircraft in Saipan and Guam. The loss of these Japanese planes certainly depleted the amount of air cover provided from their Mariana airfields.
The Japanese fleet was also detected before the naval battle. U.S. submarines were among the first to spot the Japanese fleet heading for the Marianas. In addition to this, U.S. code-breakers filtered through details of the Japanese fleet's approximate position as it closed in on Task Force 58. As such, Task Force 58 was provided with suitable details of the approaching Japanese ships, and began planning for a naval encounter with the Japanese around the Marianas.
The first sortie towards the American carriers resulted in high losses for the IJN. Of the hundreds of planes launched, only a relatively small minority returned. The heady days of the Japanese A6M were now over, and new aircraft that the Allies had introduced in the Pacific War such as the F6F provided the U.S. Navy with the best fighter plane.
Further IJN sorties launched were also ineffective. U.S. planes wiped out many hundreds of Japanese aircraft out during the sorties, which denied Japan's carriers of air cover. After the Japanese sorties, the Americans launched their bombers towards the enemy carriers. Dive-bombers and torpedo planes took off from the U.S. carriers and hit three of Japan’s carriers. Under such an aerial bombardment, the carriers could not stay afloat.
The best plane at the battle was the F6F, which was among the first Allied aircraft that eclipsed the A6M Zero. Estimates suggest that these took out Japanese planes at a ratio of 19:1 during the Pacific War. Thus, when hundreds of A6Ms and F6Fs met at the Battle of the Philippine Sea, there could only be one winner in what became something of a turkey shoot.
The U.S. planes also had another tech marvel, that of greater radar support. The U.S. Navy equipped its ships with more advanced radar detection. With their radars they detected approaching IJN aircraft some time before they actually arrived at targets. The U.S. Navy could then send out its own aircraft earlier to intercept the enemy planes more quickly. During the battle few of Japan's aircraft reached their potential targets, and no U.S. naval vessels were lost.
Consequently, the IJN had little option but to retreat from the Marianas. The Battle of the Philippine Sea was a decisive victory for the Americans that wiped out hundreds of Japanese aircraft, which combined with the more advanced Allied planes provided the Allies with clear air superiority in the Pacific. The battle was a ‘Mariana turkey shoot’ for the Americans.
In addition to this, Saipan was now open to an Allied landing. During the Battle of Saipan the U.S. Marines defeated the Japanese army stationed there, so Saipan and the Marianas fell to the Americans. The fall of Saipan was then followed by the fall of the Philippines, which left the Japanese Empire close to defeat.