Part of instructions to his marshal when Imam Ali (a) sent him to a battle 1
When you proceed towards the enemy or he proceeds towards you, the position of your force should be on the approaches high ground or on the edges of mountains or the bends of rivers, so that it may serve you as a help and a place to return to. Your encounter should be from one side or two sides. 
Place watchers on the peaks of mountains and the raised sides of the high ground so that the enemy may not approach you from any place, whether of danger or safety. And know that the vanguard of an army serves as their eyes, and the eyes of the vanguard are their informers. Beware of dispersal. When you halt do so together and when you move you should move together. When night comes fix your spears in a circle and do not sleep except for dozing or napping.