Back when all we had was Classic, I tried out a game where Germany and Russia were pals and they fought against USA, UK and Japan. The Germany/Russia combo was pretty devastating. They rather quickly over ran the rest of the Asian continent and most of Africa, although Russia had some problems with Japan because Japan kept using their transports to drop off troops all along the coast and Russia didn’t yet have enought to put garrisons in each coastal territory.
As powerful as Germany got by taking most of the Middle-East and Africa, they had a hard time trying to get at England because the Brits kept buying aircraft and sinking all the German ships. So while Germany had lots of troops and tanks, they couldn’t keep ships to take them to England. Also, Germany had put so many men along the coasts that America had to build a really huge invasion fleet to get over there. They also had to be careful about staging their ships because Germany had a lot of Luftwaffe too.
It took a while, but Germany and Russia eventually won. Russia finally got some planes over to sink the Japanese ships and Germany eventually whittled down the RAF enough that they started to keep and build a decent navy. They also used lots of subs for fodder (remember back then planes could hit subs anytime). The big American invasion took too long building and ended up being used to liberate England instead of attacking somewhere in Europe. Germany had enough guys and transports to re-take England and after a couple of large naval battles, managed to reach North America and had enough transports to keep shuttling men and tanks from Europe to England to Canada, with even a few Russian troops sent over by their puny navy to take defense hits by US counterattacks. Eventually, they even overwhelmed Eastern US. Japan couldn’t help because every time they put ships in the water, Russian planes would sink them.