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Abu Ishaq Muhammad, also known as al-Mu'tasim, was the eighth Abbasid caliph who reigned from 833 to 842 CE. His full name was Abu Ishaq Muhammad ibn Harun al-Rashid, indicating that he was the son of the famous caliph Harun al-Rashid. Al-Mu'tasim was known for his military prowess and his establishment of a powerful army composed of Turkish slave soldiers, known as the Mamluks.