I've never used horse archers a lot (except when I rarely was Mongols) But in my last game, they REALLY showed their worth: Alexander DoW'ed me in pretty early game (gee, was I surprised ) He went after a city on a great city site with 10-12 units consisting of 4-5 cats, 2-3 swords and 4-5 phalanxes. I only had 1 archers and 1 axe in my city, so I was like: "SHIIIIT!". Luckily, the borders of my city was big, so I had 3 turns before they reached my city, and a little more before they would have bombarded the defences. Without construction, I couldn't get cats to cause collatoral dmg, so I had to think of something else. Suddenly I thought of horse archers, so I quickly traded me to Horseback Riding with Isabella (same religion, my buddy ) Well, I whipped some horse archers very quick and had 6 of them when they reached my city. I gave them all that reatreat promotion and attacked. And then they showed their totally brilliance. They was about 50 % chance of winning every fight = dmg to the cats. If they lost, they reatreated (40 % chance) = dmg to the cats. Suddenly, my 6 horse archers totally demolished the whole stack without me loosing even 1. They got great xp, and Greece suddenly wasnt a threat. A little later, they came with another stack a little larger with 4-5 spears. My group of now 10 horse archers totally demolished that one too. I lost 2 horse archers Man, in the early ages, horse archers RULE for defending against stacks with cats. Also their quick movement, so u can just have a stack of them in the middle of your empire. Well, a little experience/tip from me thx (btw, I'm an emperor player, and it works gr8 there).