Replies

What would have happened if the Japanese didn’t attack Pearl Harbor? Would they have taken Australia and then India? How would that have affected Britain? If Britain and her colonies had been defeated, how would that affect the War in Russia? Germany would have been totally focused on Russia and would have had lots of oil.

The US battle fleet would have steamed gloriously forth from Pearl Harbor under some variation of War Plan Orange to reinforce the Philippines. And would have suffered the same fate as HMS Repulse and HMS Prince of Wales ...

However, the Japanese never intended to, indeed knew they couldn't, conquer Australia and/or India. What they wanted to do was establish hegemony over the Western Pacific (the Greater East Asia Co-Prosperity Sphere) by driving the colonial powers out.

The plan was to destroy the US fleet, buying enough time to seize and hold the real estate they wanted to (Yamamoto's "I'll run wild for 6 months" comment). After that they presumed that the US, UK, French, Dutch, etc would be willing to negotiate to end the war, leaving Japan as the supreme regional power.

What, with a few exceptions, they did NOT do is launch the attack with any comprehension about the US's attitude towards waging righteous war. Yamamoto was one of those exceptions - he was a realist who did his duty, did it well and fully, but still did it grudgingly.

So the result is going to be largely the same. The only wrinkle might have been that, with the US fleet wiped out on the way to the Philippines Kido Butai might have returned to destroy the naval facilities at Pearl (but they could only bomb, not invade and seize the Hawaiian Islands). Which would have forced the US Navy (both the prewar survivors and all the new ships coming on line) back to the West Coast for about a year. But the overall duration of the Pacific War would probably be about the same because even with a year's delay the Atomic Missions could have been flown from the Marianas as early as Fall 1945.