Quote Originally Posted by [b
Quote[/b] (Drake @ May 26 2004,14:19)]Infantry units like Janissary Heavy Infantry or Chivalric Men-At-Arms gain from having deep ranks as it gives a small morale boost. By having deeper ranks the ones at the front have less chance to flee in terror so kinda get pushed on the enemy. Deeper ranks therefore equal braver troops, though to be fair the ones at the front don't really have a choice.
Unit morale is calculated on unit-basis and not on soldier-basis, so the front ranks will keep fighting as long as overall morale is OK. Because of this I don't see any special virtue in your tactic.

A wide front means a better charge, more chance of wrapping around an enemy formation and simply more swords in the fight. You only want deep formations if your formation stands a chance of being scattered, like by a cavalry charge.
There is another bonus to a deep formation: in a deep formation only the front rank fights, so the unit tires less. The effects of fatigue are calculated too on unit basis, so it means that the men in front will keep fighting even though they should be exhausted (while the men in the back get tired while just standing there and doing nothing). And the reduced fatigue also makes the fatigue penalty for morale less.

But whether the effect is enough to compensate for the reduced combat ability of the unit (less men are effectively fighting) ?