When I battle I maneuver my troops back and forth a lot, especially when its battle where there are enough units to bring in reinforcements. I prefer to keep my units in formation and on a hill or forest so after a wave of enemy units I move my troops back into formation and onto a hill to wait for enemy reinforcements. However, sometimes when I move my units back, some of them rout. For example, I use my horse units to chase down routing enemies and after they pass a certain point I bring them back, lest they run into enemy reinforcements while chasing the routers down. All of a sudden they rout. What the hell? It says too many retreats but I was just returning them to their positions.

Another case would be when I would use my cavalry to bait the enemy troops. Wave after wave I would do this and then my unit would rout. Again it says.. too many retreats. I'm trying to use a legitimate tactic and my units rout? Am I doing something wrong?

Why exactly does this happen and how can I prevent it?