[Xietor]

"Well my favorite response tactic to any large unbeatable army of any type is to create armies of stealth to whittle down their support funds by taking provinces, taxing them at 200%, fading into the wilderness to attack another province two or three away. This forces them to invest in PD, move armies around internally instead of massing them to attack someone else, and make some hard choices about budgeting for awhile. It might not be a "winning" strategy but it has been known to cause them to lose their "winning" strategy long enough to knock them off the top rung. Its a great ally-tactic."

And my favorite tactic is to mind hunt the stealth commander before he can stealth away and kill his leaderless army.