Zanj Rebellion
As the main military leader of the Caliphate, it fell upon al-Muwaffaq to meet the numerous challenges to caliphal authority that sprung up during these years. Indeed, as Michael Bonner writes, "al-Muwaffaq's decisive leadership was to save the Abbasid caliphate from destruction on more than one occasion". The main military threats to the Abbasid Caliphate were the Zanj Rebellion in southern Iraq and the ambitions of Ya'qub ibn al-Layth, the founder of the Saffarid dynasty, in the east. Al-Muwaffaq's drive and energy played a crucial role in their suppression.