It's good for getting all your men to fire at the enemy.
Most of the time the enemy line infantry will just move one rank into your firing arc, so only your first rank fires then reloads. quite ungly...
[Edited by ChrisMJ, 3/14/2009 9:56:18 AM]
Oh and it's not a target ability
[Edited by ChrisMJ, 3/14/2009 10:05:04 AM]
When you research further, you gain the ability to fire three ranks deep.
Edit- and when you get platoon firing, your infantry is as invincible as invincible can be on the battlefield.
[Edited by Dhampy, 3/14/2009 10:08:15 AM]