Al-Mustansir Billah was born in 588 AH from a Turkish slave-girl. His grandfather, Al-Nasser, used to call him the judge for his abundance of mind He was pledged to the caliphate in Baghdad after the death of his father in 623 AH. Dissemination of justice and fairness in cases. He honored the people of knowledge and religion and their closeness, and established mosques, schools and hospitals, and worked to gather armies to defend the Islamic state. He built Al-Mustansiriya School in Baghdad on the coast of the Tigris from the eastern side, and the gathering of great soldiers and armies was not the same for Bani Al-Abbas. The days of Al-Mustansir in God and the glory of the caliphate lasted his days.