[cgbg]

“What if” is always difficult, but if the Japanese had not attacked Pearl Harbor there could have been nothing but minor skirmishes in the Pacific between the US and Japan for months if not years—the US would have stayed out of the war during that period (due to popular opinion against the “foreign war”) and the British would have been doomed.

“Who benefits” is always a good starting point for unraveling mysteries.

We probably would have been dragged into the war eventually—but we did not get to choose the time and place.

[Billthedrill]

Correct you are, "what if" benefits from hindsight, but it's still fun. Victor Davis Hanson makes an interesting point in The Second World Wars - by December 1941 Japan could have achieved all her immediate strategic aims without starting a war with either the U.S. or Great Britain, her two principal naval rivals in the world. Simply do what they did end up doing: marching down and capturing the Dutch East Indies' oil fields but without attacking Pearl Harbor, the Philippines, or Singapore. Done deal - it took them about three months. The Dutch could not have stopped them since they had been under Nazi occupation for a year and a half by then. Would the "Europe first" Roosevelt and the understandably Europe-first Churchill have declared war in reply given that none of their assets were attacked and that they were focused on the other side of the world? Highly doubtful.

The problem, of course, is that broad Japanese strategic planning had a far more ambitious objective: the formation of a Greater East Asian Co-Prosperity Sphere with the Philippines especially anchoring the defense perimeter. This set of plans was both elaborate and very inflexible, too bad for Japan since the world had changed radically since September 1939.