Good point. I seem to remember when keeping more current units was a new change to Civ 4 BTS AI. Or maybe it was to the Better AI Mod. I don't remember anymore but Civ 4 had a similar problem for a long time. In Civ 3 I remember getting attacked by some civ and they came at me with several stacks of 30-50 units in each stack. Since I only had 15 or so units I assumed I was going to lose but mine were calvary and theirs were warriors and archers. I actually survived because the AI was doing the same thing this AI does. Wandering around with its units (or SoD in this case) scattered - not actually performing a concerted attacked on any city. After enough turns, I wiped out their units. I think it's been said already but bad AI like that may have been acceptable with SoD but now with 1UPT it is not.