The Arabian tribal system was exceedingly complex and any attempt to describe it in all its intricate and subtle detail faces considerable difficulties.
Each tribe held sway over a roughly defined geographical area within which it controlled the pastures and water-holes and through which other tribes could pass only with its permission or by force of arms.
Most tribes were formed centuries ago when a powerful family in a particular region succeeded in establishing its own groups of followers. If, on the death of the head of the family, there was more than one son with his own following, the tribe might divide into sections. The original division would continue down the generations, usually with one section establishing itself as dominant and, as time passed, further subdivisions could take place.
As a result, there are innumerable tribes.