Quote Originally Posted by evil_maniac from mars
Well, I figure if the Holy Roman Empire has utterly decimated the combined armies of Poland, Turkey, Novgorod, and assorted rebels, and annexed them, I feel that a large garrison in the east wouldn't be tipping realism much farther...
Well, the question here is just how large a garrison you think of.
Perfectly viable (from my PoV, of course) to have, say, 400-500 men garrisoned in a critical provice, or even a full stack (960 men) in a chokepoint province. Having three full stacks in nearly all provinces bordering Khazar and Georgia is something entirely else. In my first campaign I was able to counter the Mongol threat only because my armies were accidentally in this region, forming a mass force in Khazar to attack Georgia (then Byzantine-controlled). Come to think of it, the Mongols just have had a massively bad luck back then