The Pacific War that began in the early 1940s ended in defeat for the Japanese Empire. The Japanese Empire had all but crumbled, with little left of an empire that previously stretched from Manchuria to New Guinea. Historians debate whether this was a war that Japan could ever have won, so there are a few factors behind their defeat.

First consider that the very first bombs that Japan dropped at Pearl Harbor did not do enough on the first date. At Pearl Harbor the four American carriers that were the primary target of the Imperial Japanese Navy were not present. The abandoning of a potential third wave of Japanese aircraft also spared other notable targets at Pearl Harbor such as its oil depots. So the bombers also missed a few of the best targets.

Those four US aircraft carriers stationed at Pearl would be invaluable to the decimated American navy in 1942. For this was not a war that required battleships, but aircraft and carriers at sea that had greater distance and could also provide greater support for land battles. Had these carriers been at Pearl Harbor they might have been lost, and this would have provided Japan with a greater advantage in 1942.

As it was, the aircraft carrier naval battles that did emerge in 1942 went the Allies way precisely because those carriers had remained intact. At the Battle of Coral Sea, and then the Battle of Midway, the Japanese carrier fleet would be decimated by those that had survived at Pearl Harbor. Hundreds of Japanese aircraft were lost, as well as five aircraft carriers, and the strategic targets of Port Moresby and Midway Island remained with the Allies. Much of this was done at the decisive Battle of Midway, which is the battle that some say had the most impact in the war. Had the American carriers been wiped out at Pearl Harbor, then Japan might have won such battles.

Pearl HarborCredit: This is a public domain image from Wiki Commons.
The Pearl Harbor photo above is a public domain image from Wiki Commons.

The survival of crucial US carriers may have been one key factor in the eventual Allied victory, but not the only factor. Allied cryptographers played a part in Japan's defeat. The cryptographers may have been asleep before Pearl Harbor, but hereafter they awoke and deciphered Japanese codes soon after. This was a key factor in the Battle of Midway, as the Japanese plans were no secret the U.S. were able to send a suitable carrier fleet out to Midway in advance. Hereafter, such cryptographers would continue to provide the Allies with invaluable details about future Japanese battle plans and fleet movements.

Allied subs were another factor in Japan’s defeat. While the Japanese largely neglected submarines which were primarily for surface fleet support in the IJN, the Allied subs blockaded Japanese supplies. As the subs expanded in number, so too did the effectiveness of the blockade as it sank more Japanese merchant ships, as well as oil tankers and troop transport ships with potential reinforcements.

Planes were essential to the Pacific War, and the Allies gained crucial air superiority thanks to new and more advanced aircraft models such as the F6F and F4U. While the A6M gave Japan an advantage at the beginning, by 1943 the new Allied aircraft were downing Japanese planes in increasingly large number. This culminated in the Battle of the Philippine Sea where Allied aircraft outclassed Japan’s obsolete planes, and hundreds of Japanese planes were lost during the battle along with their carriers. Air superiority would ensure naval superiority for the Allies at battles such as Leyte Gulf where much of the IJN was wiped out.

As the Allied armies advanced through the Pacific, the Japanese armies were increasingly outnumbered. Even at the beginning, they came up against larger Allied armies at Singapore. However, without such effective air and naval support victories in such battles became increasingly improbable. By 1945, Japanese armies were heavily outnumbered at Iwo Jima and Okinawa.[1] The Japanese army was notably smaller than the American army that usually had at least a 2 – 1 numerical advantage, and when they were also re-enforced by British and Commonwealth troops in some campaigns, not to mention the Chinese army in China and then later the USSR the numerical advantage was further enhanced. From a strictly numerical perspective the size of the Japanese army did not compare favorably with the combined Allied armies in the Pacific.

The Japanese had as good as lost the Pacific War after Pearl Harbor, because the US carriers were not present. These were crucial to the Allies, and ensured further Allied naval victories in 1942. As the war progressed, better Allied aircraft models, cryptography and their larger armies would all ensure victory.