In honor of the anniversary of Pearl Harbor, I wrote an article trying to explain why Japan had made such a boneheaded decision (my explanation was high-level disorganization). Commenters mostly agreed with that diagnosis, which is consistent with a lot of the things political scientists have said about Japan. But many disagreed with my assertion that Japan's war against the U.S. was unwinnable. For example, one commenter writes:
Moreover, the odds against the Imperial Japanese Navy weren't nearly so long as the ONI had erroneously calculated. The IJN quickly gained the upper hand in the early stages of the war, and would have swept the Americans from the Pacific altogether and secured Japan's hold over the Dutch oil fields but for certain shortcomings of the Pearl Harbor attack itself (with the sunk battleships proving to have been relatively unimportant targets) and but for the success of codebreakers in giving the Americans an upset victory at the Battle of Midway. Advantages in GDP and population by themselves are no guarantee of victory, especially in a naval conflict where it can take years to build fleets but only hours to destroy them.
Japan's strategy was simple: strike first, strike hard, occupy as much territory as possible, dig in, and make it incredibly expensive for the US to remove them. It was not a bad strategy, it very nearly worked. Had Pearl Harbor been a victory, had the carriers been there, had the Japanese hit the oil depots, the war would have had a very different flavor to it.
Sorry, guys, I just don't think this is the case. Here are five reasons why I think Japan could not possibly have won the war against the U.S.:
1. Size matters.
They say "It's not the size of the dog in the fight, it's the size of the fight in the dog." But that saying deserves an addendum: For roughly comparable amounts of fight, it really is the size of the dog that matters. GDP is not a deterministic predictor of who wins wars, but when you have as lopsided a ratio of war material as in the Japan/U.S. war, you basically have to be so much better than the enemy that you win all the battles.
That can happen. In the Russo-Japanese war, Japan's navy demonstrated that it could decisively defeat the Russian navy again and again. It didn't matter how many ships Russia threw against Japan - Japan could sink them as fast as they showed up. Japan's advantages in technology and training were just too great.
But in WW2, the U.S. had technology and training roughly equivalent to Japan's. The battles of the Coral Sea, Midway, the Eastern Solomons, and the Santa Cruz Islands showed that over time, clashes between the two nations' carrier fleets would result in significant attrition for both sides. That meant Japan was doomed, because while the U.S. could afford to suffer attrition, Japan could not. Game over.
2. U.S. technology never stopped improving.
At the beginning of the war, Japan held several technological advantages over the U.S. Its Mitsubishi A6M Zero fighters were better dogfighters than anything the Allies possessed. Its Type 93 Long Lance torpedoes outranged the torpedoes on American ships by a factor of about three to one. And Japan's night optics allowed Japanese ships to spot American ships first (actually this was a combination of technology and training, because the U.S. focused on radar instead of on trying to train the best night spotters). These latter two advantages were key to Japanese victories at the Java Sea, Savo Island, Tassafaronga, and Kolombangara. Meanwhile, 1942-vintage U.S. technology had some major weaknesses, in particular torpedoes that went too deep and failed to detonate.
But because the U.S. had big research budgets, and focused on technology over training, by late 1943 the U.S. had amassed a huge technological advantage over Japan. Radar advanced to the point where hit-and-run attacks left Japanese surface ships largely at the mercy of their American counterparts, as demonstrated in the battles of the Vella Gulf, Cape St. George, and (to a lesser extent) Empress Augusta Bay. By this time, of course, the U.S. had torpedoes that worked.
In the air, the U.S. built the Grumman F6F Hellcat, which took advantage of a totally new type of aerial combat ("boom & zoom" high-speed attacks, pioneered by the Germans) that replaced dogfighting. The Hellcat had much better speed and armament than the best Japanese planes, and made short work of the legendary Zero.
Radar also allowed U.S. fighters to coordinate much better, giving them an insurmountable advantage in battles like the Philippine Sea. U.S. signals intelligence was also way beyond that of Japan,
There were many other examples of U.S. technological advantage, e.g. the nuclear bomb. In comparison, Japan made relatively few advancements over the course of the war, and its much smaller manufacturing capacity meant that it could not afford to deploy the advancements it did make on a large enough scale to make a difference.
3. The U.S. was able to take even the best-fortified positions.
Time and time again, the U.S. demonstrated that it was able to take even the best-fortified positions from the Japanese military. The strategy of "island hopping" - starving out islands instead of storming them - dramatically cut down on the number of assaults the U.S. had to make. But when the U.S. did make assaults, it always won. If you can overrun positions while taking less casualties than the defenders, and if you have more resources than the defenders, it's game over.
The only battle in which a U.S. assault cost the U.S. more casualties than it cost Japan was the battle of Iwo Jima (of flag-raising photo fame). But even in that case, most of the U.S. casualties were wounded, and most of the Japanese casualties were KIA, so the Japanese resource loss was probably higher.
In other words, digging in might have slowed down the U.S. - it did slow down the U.S. - but it never would have been decisive.
4. The U.S. had oil, Japan did not.
The whole Pacific War began over oil, which Japan needed if it was going to continue conquering China. The U.S. had tons of oil, and was by far the biggest oil producer at the time. Japan, in contrast, had only the oil it managed to seize in Southeast Asia. This oil shortage chronically limited the mobility of Japan's navy, and also limited the amount that the Japanese Army could rely on tanks.
Many have suggested that Japan's critical mistake was not to destroy the U.S. oil infrastructure at Pearl Harbor - indeed, Chester Nimitz said that if they had done so, it would have prolonged the war by two years. He was probably exaggerating, but even if not, the fact is that it would not have affected the outcome of the war. Since the U.S. produced so much oil - almost a quarter of total world production in 1937 - it would have eventually brought those resources to bear.
5. China was unconquerable.
"We could only control the cities and railroads," lamented a Japanese friend, recalling the Japanese invasion of China (in which his grandfather fought as a high-ranking officer). The immensity of China - a country with six hundred million people and few natural resources - meant that Japan's attempt to conquer that country could never have succeeded. When Japan invaded China, the country was in a period of extreme chaos and civil war, and Chiang Kai-Shek's nationalists were forced to fight a rearguard action against Mao Zedong's communists even as they tried to hold off the Japanese. Nevertheless, by 1939, the Chinese nationalists had begun to win battles.
This doesn't mean the Chinese military was ever more effective than its Japanese counterpart - even late in the war, Japan won a pitched battle against the Chinese in Operation Ichi-Go. But what it does mean is that Japan suffered massive attrition against China, and with China's enormous population advantage, that couldn't go on.
The fact is, this is not some crazy revisionist history or 20-20 hindsight on my part. Japan's military leaders knew in 1941 that, barring a U.S. political collapse or coup or wholesale unwillingness to fight, they were going to lose the war.