Poopy's army is a good balanced all purpose formation. I like to put the spearmen on the flanks of the main line if the enemy has calvary, plus one in the middle just in case they launch a calvary charge on the center. It's really the composition of the enemy army that determines how you tweak the basic formation. Heavy calvary is no good against an army of spears and polearms, spears and polearms are no good against elite infantry, high quality archers in good defensive terrain - oh, oh... Rock, paper, scissors...

I do love light calvary - Alan Mercenaries, Saharan Calvary, horse archers... Their speed on the battlefield give them an added dimension that other units can't have. Sometimes my favorite part of the battle is when my light calvary are chasing down and slaughtering routed archers, crossbowmen, and infantry. An all infantry/spearmen army cannot inflict those kind of mass casualities on a fleeing army. Light calvary can lurk on the edges of the battlefied or behind the enemy and take out catapults and ballistas in the rear areas.

Those annoying horse archers - boy they're great when they are on my side - talk about a multi-capable units. They shoot, they're fast, and they're smart. They try not get into fights that they can't win, but when your back is turned they get ya..