Incidentally, I'm not sure that prisoners aren't still 'taken' in Rome. Remember in Medieval, if the enemy took prisoners but you won the battle you would get them back? Something similar happened last night.

I was playing as Carthage, attacking the Numidians. My hired horse mercs were stupid and routed almost instantly, but got hit by Numidian cavarly as they ran. They were killed almost to a man. (like 5 got away)

But I ended up winning the battle. Lo and behold, my mercs were back to 51 guys! Almost the whole unit was restored!

Now I know that not everyone who falls is 'dead,' and that some casualties can be recovered, but 80% of a unit seems a little extreme. So I wonder if they weren't 'taken prisoner' as per the old algorithm?