defensive posture

[agmoss99]

I'd say column. It has more of a defensive bonus than a line. And when disordered it is easier to move than a line. A line packs a punch in defensive fire to be sure, but you can't guarantee it will fire with ADF checked.

Of course, changing formation in the face of the enemy may lead to disorder, or even rout.

Oh and a little known point. Stack a skirmisher with your unit. With luck, if your unit is attacked in flank, the skirmisher will rotate and fire at the attacker. If so, the flank melee bonus of the attacker is eliminated.