[@HeySeuss] Exactly, its always much cheaper to encourage the internal enemies of a hostile power and provide them with the quiet assurance that you will recognize their government in exchange for alliance. Classic Stasis in the since Thucydides would recognize. It isn't that a ground invasion is impossible, and a small ruthless force can accomplish alot, but the logistics of a drawn out ground war favor the defender immeasurably.

The two major powers probably don't like to sell top of the line units to their 'allies' however, lest they decide that the friendship of one faction or the other is too expensive.