Bahman had organised a new army, made up partly of the survivors of the Battle of Ullais, partly of veterans drawn from garrisons in other parts of the Byzantine Empire, and partly of fresh recruits. This army was now ready for battle. Apart from the defeat at the Battle of Ayn al-Tamr, the incensed Arabs of this area also sought revenge for the killing of their great chief, Aqqa ibn Qays ibn Bashir. They were anxious, too, to regain the lands which they had lost to the Muslims, and to free the comrades who had been captured by the invaders. A large number of clans began to prepare for war.

Khalid decided to fight and destroy each imperial force separately. The exact location of the imperial camp at Muzayyah had been established by Khalid's agents. To deal with this objective he designed a manoeuvre which, seldom practised in history, is one of the most difficult to control and co-ordinate-a simultaneous converging attack from three directions made at night.

Khalid ibn al-Walid issued orders for the move. The three corps would march from their respective locations at Husaid, Khanafis and Ain-ut-Tamr along separate routes he had specified and meet on a given night and at a given hour at a place a few miles short of Muzayyah. This move was carried out as planned, and the three corps concentrated at the appointed place. He laid down the time of the attack and the three separate directions from which the three corps would fall upon the unsuspecting enemy. The imperial army knew of the attack only when three roaring masses of Muslim warriors hurled themselves at the camp. In the confusion of the night the imperial army never found its feet. Terror became the mood of the camp as soldiers fleeing from one Muslim corps ran into another. Thousands were slaughtered. The Muslims tried to finish this army, but large numbers of Persians and Arabs nevertheless managed to get away, helped by the very darkness that had cloaked the surprise attack.