Ḥasan Big Rūmlū served in the Safavid army. From 948/1541–2 onward, he began accompanying Šāh Tahmāsp (930/1524 to 984/1576) on his expeditions. He wrote a twelve volume general history, of which only two volumes are extant, entitled Aḥsan al-tavārīḫ, also referred to as Muntaḫab al-tavārīḫ. Of the volumes of Aḥsan al-tavārīḫ that remain are ones that cover the 9th/15th century and the 10th/16th century. The volume that roughly corresponds to the 10th/16th century focuses on the reign of some of the early Safavid rulers and is considered to be one of “the best authority for the reign of Šāh Tahmāsp”. The work was completed ca. 985/1577–78.