For some reason the two main enemies of World War 2 never seemed to want to help each other out. There wa snot a single battle that Germany and Japan fought along side one another in. If the two had actually cooperated then I bet they could of put on a much better fight.
The problem was that they were totally isolated from one another. To unite they would either have had to carve up the Soviet Union or conquer either China or India and then take over the Middle East. Looks good on Risk but by the time that happened the Allies would have sued for peace.