In the early days of Islam there was no standing army. On the occasion of any battle contingents were raised from the various tribes, and such contingents were disbanded when the battle was over. No regular salaries were paid to those who fought. Those who took part in a battle were compensated by the distribution of the spoils of war among them. Organization of the army as a State department
The army was organized as a State department under Umar. A register of male adults who could be called to war was prepared tribewise, and a scale of salaries was fixed. All registered men were divided into two categories, those who formed the standing army, and those who lived in their home,, but were liable to be called to colors whenever necessary.
Military centers called "Jund" were set up at Kufa, Basra, Fustat, Damascus, Jordan and Palestine. Cantonments were established in important cities of strategic importance. Here barracks were constructed for the residence of troops. Big stables were provided for stabling the horses and other animals of the army. A separate commissariat department was set up to attend to the food supply problems of the army units. Pay was paid to the army in the month of Moharrum. The allowances were paid at the harvest time. Every tribal unit was under a tribal leader called 'Areef. A group of 'Areefs was in turn placed under the command of an Ameer-al-Ashar.