38. The Abbasid Brothers’ Civil War
In 811, Abbasid Caliph al Amin gathered an army of about 50,000 men, mostly infantry, and sent it to put down his elder brother in Khurasan. They ran into a much smaller army of al Ma’mun, of about 5000, but they were all cavalry – mostly mounted steppe archers.
Al Amin’s army was routed, and al Ma’mun then went on the counter-offensive, invading his brother’s heartland, and besieging him in Baghdad. After a siege that lasted a year, Baghdad fell, and al Amin was captured and executed in 813. Al Ma’mun succeeded him as Caliph, and ruled until his death in 833.