Alright, so i gave this another try. Went about things reeaaal careful-like. Cancelled my alliances to pahlava and KH and made an alliance with AS, providing them with regular tribute. I had Haomavarga and Baktra, and was taking things slow and steady, building my economy and military infrastructure.
And then AS besieged me. I have two towns and, accordingly, a puny army. I'm all for difficulty, but there is literally nothing you can do.

Putting someone in a giant blender and telling him to try to stay alive as you turn it on isn't "making things difficult", it's murder.