The Byzantines came again three years later in 654 C.E. The Byzantine fleet comprised as many as 500 vessels. Against this strength the Egyptian fleet had 200 vessels only. The Byzantine fleet was commanded by the Byzantine Emperor Constans in person. To start with, the archers from each side shot arrows at the other side. This led to some damage on the sides. Then the fleet of the two sides moved closer until their masts came to touch one another. Because of the proximity of the masts, the battle came to be known as Zat us Sawari the battle of the Masts. As the two fleets came to touch one another. A fierce hand to hand fight with swords and daggers took place on bored the ships. In this type of warfare the Muslims commanded superiority. There were heavy casualties in the Byzantine camp, and the Byzantines suffered defeat. Intense booty fell into the hand of the Muslims. So great was the slaughter that the sea was virtually dyed with the blood of the wounded and the dead. So great was the remorse of the Byzantine Emperor Constans at his defeat that he did not have the courage to return to Constantinople. He sought refuge in the island of Syracuse, but here too the infuriated people rose against him, and he was assassinated.

The battle of Zat us Sawari was a landmark in the history of Islam. It established the superiority of the Muslims on land as well as the sea. The Mediterranean Sea now became virtually a lake of the Muslims.

When Uthman came to know of this naval victory, he led a prayer of thanksgiving in the Prophet's mosque at Madina. Uthman felt happy that he had the honor of being the Caliph when the Muslims first won their naval victory, and became a naval power.