and an impostor. When Abu Musa Harun was murdered shortly after, the other conspirators decided to assassinate al-Mahdi. Possibly due to the doubts of Abu Abdallah, or because they could not agree on his successor, they delayed their action. Informed of their intentions, al-Mahdi moved first. Commanders whose loyalty was suspect were sent to missions away from the capital, and replaced by loyal ones, so that on 18 February 911, Abu Abdallah and Abu'l-Abbas Muhammad were assassinated by loyal Kutama soldiers in the caliph's own palace. News of the death of Abu Abdallah al-Shi'i spread quickly. Al-Mahdi hesitated for two days, but then executed the remaining Kutama leaders involved in the conspiracy. He also instituted a new department, the 'bureau of detection' () under the supervision of the Muhammad al-Baghdadi. Anti-Kutama riots and the uprising of the anti- In summer 911, a quarrel between a Kutama soldier and an merchant in the old Aghlabid palace city of al-Qasr al-Qadim led to an uprising in the latter. The revolt, led by men associated with the previous regime, subsided after a few clashes with the Kutama, but after enough time had passed, al-Mahdi launched purges of the uprising's leaders, which encompassed his minister Ibn al-Qadim. This was but the first of many uprisings against the Kutama, however, who quickly became hated. In Tahert, a revolt broke out that killed or drove out the Kutama garrison, and then called the Zenata under Ibn Khazar for aid. A Kutama army defeated the Zenata with heavy losses, and sacked Tahert on 1 October. Its former governor, Dawwas ibn Sawlat al-Lahisi, was recalled to Raqqada and executed. In April 912, another quarrel between the Kutama and a local merchant led to bloody clashes in the streets of Kairouan, in which all Kutama in the city were killed; the sources report 700 dead. When al-Mahdi tried to discover the leaders of this affair to punish them, he was met with silence, and had to content himself with a delegation of city notables seeking his pardon. This incident rankled with the Kutama, and coupled with the previous doubts about al-Mahdi helped spark a new uprising. A young boy, Kadu ibn Mu'arik al-Mawati, was proclaimed as the true , new s were appointed, and a new holy book written. Starting from Ikjan, the original centre of Abu Abdallah's mission, the revolt spread to the cities of Mila and Constantine,