It was on a cold day in the third week of December 641 A.D. that the battle of Nihawand began. The Persian army numbered 60,000 while the Muslim army numbered 30,000.
The Persians had the advantage of holding the high ground. They had secured their right and left flanks. In front of their forward line they planted a belt of iron caltrops to lame the horses of the invader. The Persian infantry was bound to each other in chains. These chains held five to ten men together. Equipped with splendid weapons and bound with shining chains, the Persian host looked like a mountain of iron.
The Muslim left was commanded by Noman's brother Naeem, while their right was commanded by Hudheifa bin Al Yaman. Qa'qaa bin Amr commanded the cavalry. The Persian wings were commanded by Zardaq and Bahman. Their reserve were commanded by Anushaq.
After saying the midday prayers, Noman gave the battle cry of 'Allaho-Akbar', and at the third call the Muslim army dashed forward. As the Muslim army advanced they came under withering fire from the Persian archers, and many Muslims leading the attack were wounded. As the Muslim cavalry moved forward many horses were lame by caltrops. In spite of these odds the Muslim army advanced to grapple with the enemy. The battle was severe. On both sides there were heavy casualties. The two armies disengaged themselves wnen the night set. The day's action proved unproductive. The Muslims did not feel satisfied at their performance.
The next day the battle was resumed. The dispositions of the Persian army left no room for the Muslims for any outflanking movement. There was no option with the Muslims but to launch the frontal attack. In spite of the severity of the Muslim attack, the Persian army remained unshaken. It was a grim battle leading to heavy casualties on both sides. At nightfall the two armies disengaged once again. The Muslims felt unhappy. The death roll on their side was sufficiently heavy, and yet no tangible results had been achieved.
Noman now felt that as the Persians stood secure in their fortifications, a frontal attack against them would not be productive.
The strategy of Noman was that the Persians should come forward outside the security of their fortifications, so that they might be engaged in the open. The Persians were cognizant of their advantageous position, and they did not move beyond their fortifications.
For the next two days there was no action. The Muslims hoped that the Persians would move forward but they chose to remain at their posts. This stalemate also worked to the advantage of the Persians. The weather was intensely cold. The Persians were used to the weather and moreover they were secure in their fortifications. The Muslims on the other hand were not used to such inclement weather. Moreover as they camped in the open they suffered from the inclemency of the weather. The Persians organised raiding parties which caused considerable damage to the Muslims. These parties were highly mobile and they could withdraw hastily to the protection of their fortifications before the Muslims could take any counteraction.
In the meantime the Persian army continued to receive reinforcements almost every day. The Persian base was at Hamadan from where supplies and reinforcements came regularly. The Muslim's base was at Kufa which was considerably away, and that was also a disadvantage for the Muslims.
Thus in the first phase of the battle of Nihawand, the Muslims failed to produce results as all advantages lay with the Persians.