 In early 872 Mansur ibn Ja'far was killed in battle with 'Ali ibn Aban's men while defending the district of al-Ahwaz.Around the same time, the caliph's own brother Abu Ahmad ibn al-Mutawakkil decided to campaign against the Zanj and set out for Basra; he was able to capture Yahya, who was sent to Samarra and executed, but the Zanj leader defeated his forces in battle, and the outbreak of disease in his camp compelled him to withdraw by early summer.Thereafter the government scaled back its campaign to defeat the rebels, and contented itself with attempting to stop the spread of the revolt.