Board Thread:Official Discussions/@comment-1824272-20140518045610/@comment-4503347-20140518174221

The war in Ace Combat 6 is called Emmeria-Estovakia War, aka EE War (エメリア･エストバキア戦争 / EE戦争, source)

The war in Ace Combat X is supposedly called Aurelian War (Website, look for ワールド・ニュース, then you will see "A Review of the Aurelian War").

In Ace Combat 04 the war is simply known as Continental War (source).