Islamic Studies
Caliphate & Rulers: From the Rightly Guided Caliphs to the Ottoman Caliphate
Which Abbasid Caliph introduced Turkish slave-guards and made Samarra the new capital?
Explanation
Al-Mu'tasim Billah (218–227 AH) introduced Turkish slave-guards into the army and moved the capital from Baghdad to Samarra.
Reference: Islamic Studies - Caliphate & Rulers
, Page 8