You fellows need to locate an old computer game called Command HQ. They had four or five scenarios. The first one is WWI, with only ground units, transports, subs and destroyers.
The second scenario is WWII, and they add aircraft carriers and planes. The third is a sort of WWIII scenario. The fourth is a random scenario where you just start with one city as the capitol and you opponent has only one city as a capitol. This is the basic “expand faster than your opponent” game.
This was one of the first RTS war games ever written whre you can play a human on another computer. It was clearly inspired by Axis and Allies.