Imam Ali (AS), in his advice to Ziyad b. al-Nazr, said, ‘Know that the forefront of the people are their eyes, and that the eyes of the forefront troops are their vanguards; so when you leave your land and approach your enemy do not hesitate to send the vanguards to every side and to some mountain passes, woods, hiding places and every side, lest your enemy attack and lie in ambush for you.