By the time the Persian forces reached Kazima, they were thoroughly exhausted. Khalid allowed them no time to rest. As the Muslim forces were already deployed for battle, the Persians were forced to go into action. The Persian forces were linked in chains, and it was the use of these chains, which gave the battle of Kazima, the name of the "Battle of Chains."

Duel between Khalid and Hormuz. The battle started with a duel between the army commanders. Hormuz ,Commander of the Persian forces, stepped forward and invited Khalid, Commander of the Muslim forces, to a duel. Hormuz instructed some of his men to remain close to him, so that when he gave a signal they should fall on Khalid and kill him. Hormuz and Khalid began to fight with swords and shields. Both the Generals were expert swordsmen, and the fight with swords proved to be a drawn battle. Thereupon, Hormuz suggested that they should drop the swords and wrestle. When the wrestling match was in full force, Hormuz gave the signal to his men to step forward and kill Khalid. Khalid realized the gravity of the situation. He was without sword and shield, and was obviously at the mercy of the Persian soldiers. Khalid, however, did not lose nerve. He held Hormuz fait in his grip, for as long as he held Hormuz in his grasp the other Persian soldiers could not harm him. In the Muslim ranks, a warrior Qa'qa'a bin Amr saw through the Persian game and decided to take immediate action. He spurred his horse and rushed to the spot where Khalid and Hormuz were wrestling. Before the Persians could realize, Qa'qa'a had killed all the Persians who had treacherously conspired to kill Khalid. Having been freed from the threat of the Persian soldiers, Khalid tightened his grip on Hormuz. Within a few moments, Hormuz lay motionless on the ground. Khalid picked up his sword, and drove it into the body of Hormuz.

Battle of the Chains. After having killed Hormuz, Khalid ordered an immediate attack on the Persian forces. The death of Hormuz had demoralized the Persians, but nevertheless, they fought hard. The Muslims assailed vehemently, but the chain-linked Persian infantry withstood all attacks. The Muslims redoubled their attacks, and the Persians were forced to fall back. The Persians found their chains to be a death trap, and as they retreated held together in chains they were slaughtered in thousands. Before night set in, the Muslims had won the battle.

Consequences of the battle of Kazima. In the battle of Kazima, which was the first confrontation between the Muslims and the Persians, the Persians so proud of their power met a humiliating defeat. Thousands of Persians were killed, and thousands of them were taken captive. The war booty that fell into the hands of the Muslims comprised wagons, armor, stores, costly garments, horses and a good amount of money. Four-fifth of the booty was distributed among the Muslim soldiers and one-fifth was sent to the Caliph at Madina. So large was the booty that the share of each cavalryman came to a thousand dirhams. The booty included the one hundred-thousand dirham cap of Hormuz studded with diamonds and pearls. The Caliph offered this cap as a present to Khalid. The battle of the Chains at Kazima unchained for the Muslims the gate of Iraq. The so-called uncivilized Arabs had defeated the Persians so proud of their civilization extending over a thousand years.