So I'm typing away in the Citadel forum and realise that nobody talks about enfilade fire any more. It's become one of those ingrained things everybody should know, but not everybody does.
I don't mean to be presumptious, but if you are new to Total War, this is a very important concept, especially if you are interested in missile cavalry. One of the key advantages of missile cavalry is that they acheive enfilade much more easily than foot units. So here goes:
"Enfilade" a fancy name for shooting down the widest or longest part of the enemy formation. It's like "Crossing the T" for those of you familiar with naval combat with guns.
If you are directly in front of a unit of infantry and it's charging at you, you might think you have a nice, broad target. If you watch your battle closely however, you will clearly see most of your arrows flying right over the enemy's heads, especially if the target unit is running and even if the range is short. You will also notice many arrows sticking up in the ground in front, especially if your unit's accuracy is hurt by having to skirmish away.
By far, most misses — especially on stationary targets — are NOT, repeat, NOT wide to the right or left. They are overshoots and undershoots.
If you are "raking" the target down the wide side, your overshoots hit more men farther from the middle and the undershoots hit men closer too you. This is especially true if you have a height advantage. "Undershoots" still have a chance of hitting and "overshoots" can still land on an enemy instead of plowing into the hillside.
If a spear unit is four ranks deep and has 75 men, for instance, it's about 19 men wide. Get on the flank and shoot down the side of the unit. (You may need another unit to "pin" the target and keep it facing the same direction.)
It is perfectly possible for an archer to miss it's target unit completely but hit some other nearby unit. Obviously, if you are firing down the enemy's line you stand a much better chance of killing something, either in the unit you are firing at or in the next unit in line.
Many horse archers, particularly javelin troops, have a short range and a firing arc like a rainbow. The arrow or javelin lands on or near the target unless range is close. One reason close-range fire is deadly is because the trajectory is closer to being flat, resulting in more enfilade.
Camel gunners have long range and relatively flat trajectories, as far as I can tell. This can create enfilade fire at its finest. Reiters and mounted crossbowmen are also "straight shooters" compared to HA.
(Edited P.S.) Note that shooting from behind a unit attacks his most vulnerable spot and causes rather enormous morale penalties on the target unit. So don't pass up opportunities to shoot units in the back, despite the lower accuracy.
