Kroah, there is no need to create any code to support diplomacy at this stage but it would be nice to be able to simulate an alliance.
In the map editor it could be possible to set an alliance to an ID <alliance>1,3,5</alliance> for a major, meaning that the major will never attack a major ID in this list, ie. an ally.
This might mean a subsequent change in logic when both allies attack the same territory, one attack supporting the other and the more powerful force taking the territory, whilst the allied force returns gracefully to the start territory without becoming MIA.