Cavalry deal a lot in the first strike, monsters retreat easy. 800 cs of cavalry beating 1500 cs of monsters is impressive, but not surprising.
What stat does the captain influence? Leadership score? Cohesion?
I believe it increases a character's leadership score, by the amount shown. Leadership, in turn, influences a number of things, many of which I'm unsure of, but I believe that it does have a small effect on cohesion. I have also heard that leadership increases a unit's general fighting ability, which I would like to have confirmed or denied, if anyone is willing to share that with me.