The commander of an Arabyan army is likely to be a Grand Vizier - perhaps the Grand Vizier of the Great Sultan himself.
Few Sultans would be so bold as to take to the field personally but throughout history there have been notable exceptions, such as the mighty Sultan Jaffar who led a powerful army into Estalia and besieged the Tilean city of Tobaro. Subordinate to the overall commander are marshals and commanders of lesser rank within the palace hierarchy, noble Emirs, and Sheiks from the desert. These military leaders often ride upon Elephants as befits their exalted rank.
All Sheiks and Emirs are hardened warriors, living in the burning hell of the desert and having to constantly fight off bandits, members of rival nomad tribes, and the evil Undead of Nehekhara. They are respected and trusted by their fellow Arabyans, for their word is law and they obey without question, such is their custom. Only very rarely will another member of their warband, who is of noble birth, challenge the Commander's leadership. In these instances, single combat is fought to determine who has the divine right to lead their people into battle.