The general idea is to play the most solid, risk-free offensive moves possible. It’s based on the theory that the game is grossly unbalanced in Axis’ favor and therefore all risk should be eschewed, because assuming risk can only work in the Allies’ favor.
Unless my opponent is informed beforehand by telling him exactly what I plan to do, he will almost always go Atlantic with US. It’s not at all necessary that he does, that’s just what ends up happening. If he goes Pacific, no biggie, half the fleet is in the Philippines and can protect SZ6 as long as need be. I’ve playtested both scenarios and it’s frustrating as all hell for Allies because he can’t advance anywhere that matters, and what advances he does make are glacially slow in the execution.
The Allies always get the choice of whether to give either the European Axis or Japan a better game, by deciding which way the US will focus. This strategy accommodates either choice. If the US goes Atlantic, Germany builds defensively a bit earlier, ends up more in a stalemate with Russia, and Italy goes defensive for the whole game - but Japan runs rampant and becomes a superpower. If the US goes Pacific, Japan will still get to be large enough to hold the US off more than long enough for a Germany that builds fast land units almost exclusively to overrun Russia. I anticipate in either case Italy will be reduced to a rump player, so beating up on Italy in the Med doesn’t faze me, its only truly essential job is to hold Rome.
Doesn’t matter which poison the Allies pick, they still get the poison.