Version 5.6 - stratmap2D & battlefield3D reinforcements
When fighting a battle with reinforcements but want to leave the back up army up to the AI.
MUSTER THE HORSEMEN!
I keep a fast reaction army of horse divided up between my forts (4 at a time to quash their running costs). When I move into an attack stance or need their support in defence it is a lot easier to gather horsemen into a sizeable lump. Sometimes I can muster and field an 8 or even a 12 stack army of horse in support which I bring into the side of the NME force. I leave it to the AI knowing they will come in quick and harry the NME drawing off their focus of attack. I like seeing them from my ranks - usually just saving the day - especially if it's a seige I'm in!
After the battle, the surviving horsemen from force 'B' swell the ranks of my surviving army. This tactic is of course only to be used when you begin to face full stacks of tough NME and not on the local bandits (unless you take the young prince out with a few men and bring in one troop of horse as AI support! *horn parp!* My Lord, Rohan has come at last!