Well, maybe, but if i loose 1-2 units every time he attacks, i cant win as i will constantly have less and with a negative gold income i wont be able to build new ones aswell, hence just bleeding out.
Yeah, if you end up locked in a situation where you can't regain those territories then you're screwed. If you can weather the storm a couple of turns while you consolidate your forces and prevent your opponent facing you on two fronts you can pull out of it.