"Abu Ja'far Abdallah ibn Muhammad al-Mansur (/ælmænˈsʊər/; Arabic: أبو جعفر عبدالله بن محمد المنصور; 95 AH – 158 AH (714 CE – 6 October 775 CE) ...
usually known simply as by his laqab Al-Mansur (المنصور) was the second Abbasid caliph, reigning from 136 AH to 158 AH (754 CE – 775 CE) and succeeding As-Saffah. He is known for founding the 'Round City' of Madinat al-Salam, which was to become the core of imperial Baghdad.
Modern historians regard Al-Mansur as the real founder of the Abbasid Caliphate, one of the largest polities in world history, for his role in stabilizing and institutionalizing the dynasty.: 265 " - (en.wikipedia.org 12.12.2021)