By maintaining economic control.
1. Neuter Italy. Without a north african/middleeast campaign OR sea lion, the axis will never outproduce europe economically.
2. Stack Australia, Hawaii, with ground units and planes. play PREVENT against the Japanese victory, and when you can, pick apart their navies, or islands. If you’ve delayed the capture of India post J4, you are doing great. with China, keep your stack out of range of japanese planes, until UK is in the war. By going north, then coming back down south. (Unless you get specific oppurtunities to take back yunnan)
3. FAT build Russia Early, men, men, men, men, some more men, a piece of artillery, and if you get SBR’d later, add in tanks as needed. Make sure you put together a mobile middle east force, that can activate Persia the INSTANT you are at war, by coming through Kazakstan. meeting infantry that drop down to NW Persia, conquering IRAQ the next turn, and supporting England.
4. Give the axis room to expand, where into less valueable, undefendable areas, but keep them contained. Focus on detroying transports. and ground units. Find ways to negate the ability of the axis to use their airforce, by either hiding, or travelling in numbers that can’t be attacked. If that means giving up certain oppurtunities - do just that.
5. Starve them out. Without economic control, the axis will peter out. You will simply be putting more units on the board, they WILL lose.
Last… Build a trump card. Have bombers available in LONDON/CAIRO - in range of Moscow, 6 or 7 maybe, aside from causing all kinds of problems, they are an instant hit soak trump defence. You can use them to either destroy a small axis stack, or stop a final axis capital grab. Same goes in the pacific, from honolulu to queensland.
As the allies, Don’t worry about how you’re going to “win”. Just make sure you don’t lose. It’s exactly like tic-tac-toe, except the axis loses when there are no more moves left.