Ali marched with forces to Nahrawan. Reaching Nahrawan Ali planted a standard on the ground, and declared that those who came under the standard would have amnesty and safe conduct. Some persons deserted the Kharijite camp and were allowed amnesty and safe conduct to their houses. Thereafter Ali sent a message to the Kharijite asking them that should surrender the persons who were guilty of killing Abdullah b Khabab and other Muslims. The Kharijite refused to surrender any person, and declared that they would consider it to be a virtue to fight against Ali and his forces.
Ali marshaled his force and launched an attack against the Kharijites, with the battle cry "on to paradise," the Kharijites rushed on their troops of Ali. The Kharijites hardly numbered four thousand, while the troops Ali numbered about fifty thousand. The Kharijites fought desperately and frantically but they were outnumbered by the forces of Ali. Out of four thousand Kharijites, only two or three dozen Kharijites escaped; the rest were killed.
Ali won a decisive victory at Nahrawan, but it proved to be a hollow and fatal victory, which diverted Ali from his main war against Muawiyah. After the victory of Nahrawan, Ali felt that the victory would raise the morale of his people. That was however, not to be the case. Ali wanted that from Nahrawan he should proceed direct to Syria. His army, however, desired that they should return to Kufa and thereafter proceed to Syria after taking some rest. Ali agreed with the wishes of his troops. The army returned to Kufa and went to Nukhails outside Kufa. The troops given leaves for two or three days and were commanded to return to camp thereafter in order to proceed to Syria. The men left the camp, but did not return to march to Syria. Ali addressed the people in the mosque, and exhorted them to join the camp. He reproached them for their disobedience and accused them of treachery. These exhortations, reproaches, and accusations had no effect on the people, and heart broken Ali had to abandon the campaign to Syria. When we reflect at the events that happened it appears that there was something wrong with the military organization. The troops lacked discipline, and instead of obeying orders from above, the troops indulged in giving orders. The troops betrayed Ali at Siffin and forced him to stop the war when the victory was almost in sight. At Kufa Ali was betrayed by his troops again when they refused to march to Syria. This naturally led to the advantage of Muawiyah. When he got the intelligence that Ali was planning a march to Syria he led his forces to Siffin. When Ali had to abandon the campaign to Syria, Muawiyah withdrew his forces from Siffin and led them to Egypt with a view to wresting that prize province from the control of Ali. Misfortune was now stalking the footsteps of Ali. Henceforward he was faced not with the loss of territories alone, he came to be exposed to the danger of losing his life as well. Though most of the Kharijites were killed at the Battle of Nahrawan, some Kharijites escaped the massacre, and these people conspicuous for their fanaticism vowed vengeance against Ali. The victory of Nahrawan thus paved the way to the assassination of Ali, for a Kharijite assassinated Ali two years later.