Why are tactical battles mass chaos?

[Slug For A Butt]

I always figured the chaotic look to battles was representative of how people motivated to save their own lives might actually fight in a general melee. In general I should think that a medieval warrior would be more concerned with dodging a sword coming at him than he would be with sticking right next to his buddies. It seems natural then that the formation should suffer as people dodge about and do things in their own best interest.

So why was the phalanx more disciplined? Why was the maniple more disciplined? The medieval noble fought for exactly the same reasons as the Greek nobles fought. These people were in the same mortal danger, why are you suggesting that medieval soldiers had more reason to be ill disciplined?