Ertuğrul Bey and the Knights Templar in the 13th century Alba and step and step with the struggle against brutal Mongols depicts the process of establishing the Ottoman principality.Nothing is known with certainty about Ertuğrul’s life, other than that he was the father of Osman; historians are thus forced to rely upon stories written about him by the Ottomans more than a century later, which are of questionable accuracy. An undated coin, supposedly from the time of Osman, with the text “Minted by Osman son of Ertuğrul”, suggests that Ertuğrul was a historical figure. Another coin reads “Osman bin Ertuğrul bin Gündüz Alp”, though Ertuğrul is traditionally considered the son of Suleyman Shah. In Enveri’s Düsturname (1465) and Karamani Mehmet Pasha’s chronicle (before 1481), Suleyman Shah replaces Gündüz Alp as Ertugrul’s father. After[when?] Ottoman historian Aşıkpaşazade’s chronicles, the Suleyman Shah version became the official one. According to these later traditions, Ertuğrul was chief of the Kayı. As a result of his assistance to the Seljuks against the Byzantines, Ertuğrul was granted lands in Karaca Dağ, a mountainous area near Angora (now Ankara), by Kayqubad I, the Seljuk Sultan of Rum. One account indicates that the Seljuk leader’s rationale for granting Ertuğrul land was for Ertuğrul to repel any hostile incursion from the Byzantines or other adversary. Later, he received the village of Söğüt which he conquered together with the surrounding lands. That village, where he later died, became the Ottoman capital under his son, Osman I. Ottoman historians have differing opinions on whether Ertuğrul had two or possibly three other sons in addition to Osman: Saru Batu Savcı Bey, or Saru Batu and Savcı Bey, and Gündüz Bey.