The main battle began on the 8th of Safar 37 A.H. The heralds from the army of Ali stepped forward, and shouted to the army of Muawiyah to accept the truth and acknowledge the caliphate of Ali. The heralds from the army of Muawiyah shouted, "We seek vengeance for the blood of Othman. Hand us his murderers if you are in the truth". These calls proved ineffective, and the two armies arrayed themselves for action.
The army of Ali was divided into the three usual wings, the right wing, the left wing and the central wing. The central wing was commanded by Ali himself and this wing comprised some veteran companions of Madina. One wing comprised contingents from Kufa, and the other wing comprised contingents from Basra. The cavalry of the Kufa wing was led by Malik Ashtar while the infantry of this wing was led by Umar b Yasir. The cavalry of the Basra wing was led by Sahl b Hanif, while its infantry was led by Qais b Sa'ad.
Before the war began Ali addressed his army. He said that they were fighting in the cause of God, and the vindication of the truth. He exhorted his men to prove their worth by performing prodigies of valor. If they survived they would be Ghazis and if they fell, paradise would await them. He asked his men not to fire the first shot. The enemy should take the initiative, but when the war began they should not rest content till they had defeated the enemy. The men were enjoined not to turn their backs. They were exhorted to play the role of heroes. They were instructed not to attack any wounded person; not to cut the limbs of dead person; not to molest women; not to kill the aged and the children; and not to plunder. They were asked to be steadfast, talk less and fear God.
Before the beginning of the battle proper, according to the usual Arab practice the challenge to personal duel was given, Ali gave the challenge for personal combat with Muawiyah. Muawiyah did not accept the challenge. Then Malik Ashtar the Commander-in-Chief of the forces of Ali stepped forward, and gave a challenge for a personal duel with 'Amr b Al 'Aas the Commander-in-chief of the forces of Muawiyah, 'Amr b Al Aas did not accept the challenge.