Khalid drew up his 13,000 men for battle on the south bank, and he too organised his army into a centre and two wings. The left was commanded by Abu Hudhaifa, the right by Zayd (elder brother of Umar), while the centre was directly under Khalid. For this battle Khalid formed his men not in tribal groups, as had been the custom heretofore, but in regiments and wings as required for battle, with tribal contingents intermingled. Khalid planned, as was usual with him, to attack at the very outset, throw his opponent on the defensive and keep him that way. Thus Musailima would be robbed of his freedom of manoeuvre and could do no more than react helplessly to the thrusts of the attacker. Khalid ordered a general attack, and the entire Muslim front surged forward with cries of Allahu Akbar. Khalid led the charge of the centre while Abu Hudhaifa and Zayd led the charge of the wings. Khalid ibn al-Walid thought that his warriors would soon break through the enemy army, but the army of disbelief stood as firm as a rock. After some time spent in hard slogging, a slight lack of order became apparent in the Muslim ranks as a result of their forward movement and their attempts to pierce the front of the infidels. Then Musailima, realising that if he remained on the defensive much longer the chances of a Muslim breakthrough would increase, ordered a general counter-attack all along the front.
The apostates moved forward and the fighting became more savage as the Muslims struggled desperately to stem their advance. Some lack of cohesion was now felt in the Muslim regiments due to the mixture of tribal contingents which were not yet accustomed to fighting side by side. Gradually the numerical superiority of the apostates began to tell and the Muslims proceeded to fall back steadily. Then the pace of withdrawal became faster; some regiments turned and fled, and others soon followed their example, causing a general exodus from the battlefield. The Muslim army passed through its camp and went on some distance beyond it before it stopped, with the apostates in hot pursuit. The apostates stopped at their opponents' camp and began to plunder it; this gave Khalid time to prepare and launch a riposte. Khalid could see what had gone wrong. The apostate front had not given way under the terrible onslaught of the Muslims. The Muslims had lost their balance and, under the pressure of the counter-attack, were unable to regain it. Khalid saw that forming regiments out of mixed tribal contingents had been a mistake, for the clan feeling was still very strong among the Arabs. It added another pillar of strength to the Islamic zeal and the individual courage and skill which distinguished the Muslim army. In the face of the three-to-one superiority of the enemy and the blind, fanatical determination of Musailima's followers, the absence of tribal loyalty had resulted in a weakening of cohesion in the Muslim regiments.
Khalid corrected this mistake and regrouped the army. He deployed it in the same battle formation with the same commanders, but the soldiers were now formed into clan and tribal units. Thus every man would fight not only for Islam but also for the honor of his clan. There would be healthy rivalry among the clans. Once the reorganisation was complete, Khalid ibn al-Walid picked a handful of warriors and formed them into a personal bodyguard. It was his intention to set an example for his men by throwing himself into the thick of the fighting. This bodyguard would prove useful. The Muslims once again advanced to the plain of Aqraba. Meanwhile Musailima had redeployed his army in the same battle formation as before. He awaited the second strike of the Muslims.
On the orders of Khalid, the Muslim army again swept forward. The Muslims launched violent assaults all along the front. The most dreadful carnage took place in a gulley in which human blood ran in a rivulet down to the wadi. As a result, this gulley became known as the Gulley of Blood-Shueib-ud-Dam, and it is still known by that name.
But the battle hung in the balance. Khalid now realised that, with their fanatical faith in their false prophet, the apostates would not give in. It was evident that only the death of Musailima could break the spirit of the infidels; it would be a moral setback, which would lead quickly to physical defeat. However, Musailima was not dueling in front like Khalid. He would have to be drawn out of the safety of the apostate ranks in which he stood surrounded by his faithful followers. As the first violent spasm of combat spent itself, the warriors stopped to regain their breath. There was a lull.
Then Khalid stepped out towards the enemy centre and threw a challenge to single combat. Several champions came out of the apostate ranks to accept the challenge of Khalid ibn al-Walid and advanced towards him one by one; Khalid disposed of each opponent. Slowly and steadily Khalid advanced towards Musailima, killing champion after champion, until there were none left that were brave enough to come forth against him. By now he was close enough to Musailima to talk to him without shouting, and he proposed talks. Musailima agreed; he stepped forward cautiously and halted just outside duelling distance of Khalid. Khalid had already determined to kill Musailima; the talks were only bait to draw him close enough. At that instant Khalid sprang at him. Khalid ibn al-Walid was fast, but Musailima was faster. But in that moment of flight, something meaningful happened to the spirit of the two armies, depressing one and exalting the other. The flight of their 'prophet' and commander from Khalid was a disgraceful sight in the eyes of the apostates, while the Muslims rejoiced. To exploit the psychological opportunity which now presented itself, Khalid ibn al-Walid ordered an immediate renewal of the offensive. The apostates began to fall back as the Muslims struck. After some time the infidel front broke into pieces. The bulk of the army broke and fled, scattering in all directions.
Only about a fourth of Musailima's army remained in fighting shape, and this part hastened to the walled garden while Muhakim (commander of the right wing) covered its retreat with a small rear-guard. This rear-guard was soon cut to pieces by the Muslims, and Muhakim fell to the arrow of the Caliph's son, Abdur-Rahman. Soon the Muslims arrived at the walled garden, where a little over 7,000 apostates, Musailima among them, had taken shelter. The infidels had closed the gate.
The Muslims were anxious to get into the garden and finish the job. Soon a Muslim soldier asked his fellow men to let him climb the wall so that he could open the gate by killing the guards there. The soldier jumped in to the garden and opened the gate. The Muslims entered the garden and the last and most gory place of the Battle of Yamamah had begun.
The apostates stepped back as the Muslims poured into the garden. The fighting became more vicious. But Musailima was still fighting: he had no intention of giving up. As the front moved closer to him, he drew his sword and joined in the combat. The last phase of the battle now entered its climax. The Muslim army pressed the apostates everywhere and it was only the endeavours of Musailima which prevented a general collapse.
Then Musailima came under the hawk-like gaze of the Wahshy ibn Harb (the same man who killed Hamza bin abdul mutlib, the uncle of Muhammad, in the Battle of Uhud before accepting Islam). He threw a javelin and struck Musailima in the belly; the next moment Abu Dujana cut off his head. The news of the death of Musailima brought about a rapid collapse of the apostates. The garden where this last phase of the battle took place was named the "Garden of death". All the 7000 apostates were killed there. 
