Guarding thugs

[Actuarian]

If you have a decent sized group defending, it will act as a buffer between the enemy troops and the commander. This can be a particularly good if you have a HP weak magic user and/or you are fighting flying troops. Otherwise your magic user can be killed before he casts many (or sometimes any) spells.

I have used the random event generated militia for this defense. Even if their morale breaks they still are a temporary distraction for the enemy, and can make the difference between the mage surviving or dying; this in turn can make the difference between winning or losing a battle.

Assuming you place your spell casters near the back of your troops, I think this tactic should also help against enemy archers shooting at the rear by providing some extra targets.