How's this? POD starts with Japan launching a devastating strike against the Phillippines a day before the US declares war on Spain (they can see the writing on the wall and want to keep the USA as far away as possible). The US can't really complain, as it was making a case about how the Spanish were misruling their territories, but hang on to Cuba instead of letting it go free (without the Phillippines, they will want
something major to show for the war).
Cuba goes into revolt, a harsher one than the Phillippines went into OTL, and the US loses a lot of soldiers (more due to disease than the Cuban rebels). With Cuba such an eyesore, the American public just doesn't support any initiative to enter World War I. On the other side of the world, with Japan's taking of the Phillippines, Anglo-Japanese relations deteriorate (Britain is worried about Hong Kong, Singapore, and Australia), and when Japan defeats Russia in the Russo-Japanese War (Britain doesn't intervene, but cuts off trade with Japan in protest), Japan sends feelers to Germany seeking a treaty. Germany, realizing that its own Pacific territories are vulnerable, and seeing that an allied Japan would give Russia the same dose of encirclement that Germany has been feeling of late, agrees, and Japan joins the Triple Alliance, which now becomes the Quadruple Alliance. When World War I erupts, Britain, having been forced to send ships to the Pacific to deter Japanese aggression, underestimates both the Japanese forces (later studies show that the British admiralty was heavily influenced by racist beliefs of the Japanese as inferior to the British) and the Germans; an earlier Battle of Jutland, with the entire High Seas Fleet steaming out to face the significantly smaller British navy blockading Germany, is able to destroy much of the force with less than a quarter of the losses (although it is still a blow to the High Seas Fleet, the battle is a clear German victory, and the trade route into Germany from America is now opened), while the Japanese succeed in taking Hong Kong and most of Malaysia while besieging Singapore and preparing a land invasion of Australia.
The US, busy with pacifying Cuba and now able to actually trade with Germany, does not begin its pro-Entente tilt. Furthermore, without any real Pacific real estate save for Hawaii, it is not as worried about the Japanese as it was OTL (the losses of Britain are internationally attributed to the British having to divide their forces, and the belief that the Japanese are inferior holds, except in Japan, naturally). With food and supplies now able to enter Germany, Germany stops its unlimited naval warfare plan before it begins, and German U-boats gain fame for accompanying German vessels into battle and sinking battleships, rather than for annihilating shipping, although they still do this to some extent.
Japan, meanwhile, invades the Dutch East Indies, overrunning the Dutch defenders and being hailed as heroes and liberators by the natives. Australia invades the Dutch East Indies as well, and the two forces clash on the island. It quickly becomes a land war similar to those in Europe, and vast jungles are wiped out during the engagements, turning the soil into as lunar a landscape as Belgium and France. With ANZAC troops rushed in to stop the Japanese (who have total naval supremacy in the region, and use it to the fullest effect), and with the British navy defending home waters while German troops push forward, Italy joins in the war, living up to its pre-war alliance, and attacks south-eastern France. The French ship troops south and halt the Italian invasion and push it back into Italy, but a fierce German attack on the Marne succeeds with no British or French reinforcements available (the British hold back, fearing a possible German invasion, whereas the French shipped most ready reinforcements south to halt the Italians). At the same time, the Japanese, having the edge in the war against Australia, push forward, and defeat the ANZAC troops (remember, they were not nearly as war-ready as Japan, and Australian industry can't keep up with Japanese). The Great War is ended in November, and the Treaty of Hamburg changes the world.
The treaty states that Britain will recognize the rights of Japan in the Pacific, and Japan gains all of the territory that it won in the war. In Europe, France rescinds its claim to Alsace and Lorraine, and both nations agree to demilitarize the border; furthermore, Italy regains control of the island of Corsica after more than a century. In the East, Russia gives up Poland and Galicia, which go, respectively, to Germany and Austro-Hungary. Austria annexes much of Serbia, and Russia agrees to relinquish its claim as the protector of the South Slavs. France also gave up its African territories to Germany and Italy. British East Africa and Northern Nigeria goes to Germany, with British Somalia going to Italy.
With World War I a huge Japanese victory (moreso than any other nation), Japan devotes itself to building its empire. With war having succeeded to any desired point, Japan does not gain a "War Cabinet," and instead focuses on integrating the Empire with the Home Islands; having learned from the years of European hardship in quelling natives, Japan opts for friendship rather than dominance, and its system of enforcing laws absolutely and eliminating centuries-old power structures gain the favor of the populace, as does the fact that Japan is the only Asian power able to stand up against the Europeans.
By the 1930s, Japan has heavily built up its industry, awash with the resources of its empire, and life has improved in the conquered lands to such a point that most people now refer to themselves as Japanese, the connotation becoming one with "citizen of Japan" as much as American refers to "citizen of America" rather than any particular racial strand. The Great Depression never occurs, so there is no negative effect on global economy. Japan also learned very well from the war; when troops were too inland for ships to reach, Japan realized that planes can be a form of long-distance artillery, and Japanese planes in particular gained a reputation of destroying concentrations of Australian artillery with makeshift bombs. Another innovation of Japan was simply realizing something that happened in Europe, too: namely, armored cars. Japan was appalled at the trench warfare of the Russo-Japanese war, but this had been thought of as a fluke; when the same thing happened against Australia, and in Europe between Germany and France/Britain, Japan realized that basic infantry and cavalry had reached their limit. It also saw that armored cars, while new and prone to breaking down, could punish enemy infantry with little risk to itself, save for artillery hits. The vehicle could deflect glancing shots, but not major hits, and thus had to rely on its speed to move it away from trouble and its firepower to silence trouble, rather than on a "shield." This system was likened to that of the samurai, which never developed a European-style shield, but rather an intricate armor system that could deflect glancing sword-strikes and arrows, but relied on the samurai's skill with his blade and his own movement to avoid fatal blows. Thus, the armored car was refined with speed and firepower in mind, while tracks to overcome trenches and slightly thickened armor were introduced. The final product was called a
yoroi, the name of samurai armor.
The Great Depression, which strikes in 1923, heavily devastates the economies of Europe and the United States; Japan, however, has largely cut itself from the world economy, focusing its products on its own empire and building up the conquered lands to a higher level. So, although the Depression affects Japan, the blow is not nearly as heavy as in the US and Europe. By 1930, the Japanese economy has reached the US' level (which did not become an arsenal to the Entente, nor received the big boost from the entry into war by having to supply millions of troops, and thus is hurt even worse by the Depression). This makes the US stand up and notice Japan, and the US begins talks with Australia for an alliance against the Japanese. The United States also places an embargo on Japan, accusing it of mismanaging the territory illegally conquered in the Great War, which is a blow to the Japanese economy. Japan, however, is wealthy enough that militarists are not able to use the situation to gain power; the decision is made, however, that Australia is a dangerous foe, particularly with the United States supporting it. Thus, on May 4th of 1936, Japan launches a surprise attack on Australia and the United States.
In the space of the two decades since the Great War, most of Europe focused on the lessons it learned; namely, infantry movement was the key to war. Thus, the European style of war developed into a heavily mobile and infantry reliant one, with planes being designed as large as possible to deliver paratroopers, and with infantry armed with automatic rifles and machine guns. Only Japan had focused on the development of armored cars or dive bombers; thus, although the Australian infantry was able to annihilate the first waves of Japanese infantry, the situation was soon changed when Japanese takas (dive bombers) and washis (fighters) arrived. Soon, air supremacy rested with the Japanese, and the arrival of the yoroi obliterated enemy infantry positions, particularly when used in coordination with taka assaults. At the same time, most of the Japanese Navy had approached the island of Hawaii, and launched a surprise attack on the US Pacific Fleet stationed there. Although a battleship and a carrier were not at the harbor, and thus were spared destruction, the destruction of almost all of the US Pacific Fleet by the superior Japanese warplanes was a rude awakening to the Americans. The US and the British Empire declared war on the Empire of Japan on May 5th, but the fighting in Australia was harsh, and the British naval squadrons in India were ordered to wait for reinforcements from the Mediterranean before engaging the Japanese, whereas the United States now had to sail the Atlantic Fleet out to reach Japan; this was made even harder when the Kira Butai, the Japanese strike force, also attacked the Panama Canal, obliterating the passage so severely that it would take approximately seven months to rebuild.
The Japanese raikou kousen, or lightning war, annihilated Australia's ability to resist, and despite the bravery of the Australian troops, Canberra fell to the Japanese on June 17th. In the meantime, the remaining Japanese naval forces had raided the British Indian Ocean Fleet, which consisted of a carrier and 4 battleships, and the commander, wishing to avenge Britain of her humiliation in the Great War, disobeyed orders and pursued the Japanese. The Japanese ships, while no match for the British fleet, succeeded in leading the British on a wild goose chase until the Kira Butai returned to Japan on May 29th. The British fleet was then led into a trap, and the Japanese carriers succeeded in quickly targetting and destroying the lone British carrier; after air support was lost, the remaining British ships were each destroyed in short order.
Japan now prepared for true war against the Americans; only a few troops were needed to occupy Australia, whose population was not quite 9 million, and so an army of 3.7 million soldiers, accompanied by 11,000 yaroi and more than 20,000 takas and washis, as well as the might of the Japanese Navy, now the largest in the world, prepares itself to fight the US. Japan invades Hawaii on July 4th, 1936, as the United States celebrates its independence day. The fighting is again fierce, but once more the Japanese armor and surgical strikes prove themselves decisive, and air supremacy leads to victory. Furthermore, much of the island population, seeing the benefits in the lands Japan has conquered, openly side with the Japanese once victory becomes evident, and makes resistance impossible. This also speeds up the building of the island in preparation for retaliatory US strikes and conquest attempts, and Hawaii becomes the forward Japanese base of operations against the United States.
The fall of Pearl Harbor, in particular, yields a treasure trove for the Japanese; in particular, Japanese troops are able to seize the US naval code before it is destroyed, and use it to stunning effect: the US Atlantic Fleet is ambushed as it sails north towards Los Angeles, outnumbered nearly three to one, with a five to one disadvantage in carriers, and is annihilated with hardly any Japanese losses. With the US fleets out of commission (although the US begins a powerful program of rebuilding on the East Coast), the plans for an invasion of the continental United States are drawn up.
Unlike England, which was able to create a powerful defensive wall when it feared German invasion in World War I, the United States are unable to throw up sizable defenses along the massive stretch of Pacific coastline. Their mobile infantry reserves, green to the gills, are called up, and more troops are churned out by the government, with an army of nearly four million men ready to hurl back the Japanese and nearly four million more being trained. The US, however, has only a handful of yaroi, called armored cars, which are more land-fortresses than mobile weapons (the idea was that the infantry take a position, and armored cars hold it against any attackers until infantry can support them in defense). US warplanes are also designed to carry troops, and thus, although long-range strategic bombers are plenty, the US lacks both dive bombers and fighters that can come close to matching the Japanese.
And so, on September 11th, Japan invades the United States at an obscure beach in Oregon, overrunning the few defenders in a matter of hours and establishing a beachhead which is able to throw back four assaults from nearby US troops. Once again, although the Japanese infantry is not as well trained or armed as the US troops, the Japanese yaroi obliterate infantry and run circles around US armored cars, often simply bypassing the slow-moving behemoths as they fall prey to taka strikes. Portland falls to the Japanese in little more than two weeks of fighting, and the Japanese First Army strikes north into Washington, while Second, Third, and Fourth Armies strike south, into California. Washington's defenders are also unable to halt the Japanese, but as winter sets in, the Japanese advance slows in Washington, although the region is not cold enough to prevent Japanese yaroi and planes from destroying any force that comes out against them. To the south, in California, the cold weather comes slower, and the Japanese continue southwards until they reach Sacramento; it is here that the US Third and Fourth Armies have prepared to face the Japanese, and the fighting for the state capital deals the Japanese the heaviest losses they have received so far. The US, however, lacks the ability to take out the massed yaroi, which cut through any pockets of resistance, and Japanese bombers obliterate much of Sacramento before both armies surrender to the Japanese forces.
The prisoners taken so far are shipped to detention camps in Hawaii, where they are processed and then sent back to the Home Islands for "safe keeping." Furthermore, with no significant British or American activity in the Pacific, the Japanese supply route, although incredibly long, is also very secure, and supplies begin to arrive on a round-the-clock basis. Most of the supplies coming in, aside from ammunition and the like, are more yaroi; the Japanese see that the Americans have nothing to stop the yaroi at the moment, and thus press their advantage. With both armies wiped out, the Japanese are able to finish out California by taking San Francisco and Los Angeles within a week of eachother (the first falls to Second Army, while Third and Fourth take the massive Los Angeles); the Golden Gate bridge is one of the famous losses of the Battle of San Francisco, and, in a famous scene, the Japanese commanding general solemnly apologizes to the mayor of the city for the loss, stating that "all of Japan grieves at the loss of this wonder," and offering to speak with his government on reimbursement and repair of the bridge.
Having faced only losses, the American president, Charles Curtis, agrees to the Japanese demands, which are surprisingly agreeable, as per the advice of Admiral Yamamoto, the head of the Japanese navy, who advised his government that the United States could grind Japan into dust if the war lasts too long. The island of Pearl Harbor will regain its independence, and will be neutral to both the US and Japanese, who both pledge to respect the sovereignty of the nation. Everything west of the islands falls into the Japanese sphere of influence, and everything east into the American. Japan will also gain Australia and New Zealand (which it did not conquer but simply bypassed), but will pay hundreds of millions of US dollars to repair the destruction of the major American cities, and sign a non-aggression pact with the US. Curtis asks his Chief of Staff, Gen. Pershing, if the US can defeat Japan; Pershing replies, "Sir, if we can keep them talking for another year, then yes. Otherwise, they can take everything west of the Rockies, and we'll be damned if we can stop 'em."
On January 9th, 1937, the United States formally agrees to end the war with Japan; although the US itself does not call this a surrender, it is widely recognized that the beast is what it is. With its ally out of the war, Britain sues for peace as well, and is forced to recognize Japanese control of Australia and New Zealand.
(The map is of the world after World War I. Just make Australia and New Zealand yellow, and Hawaii white, and you'll have the world after the Pacific War).
