A skilled commander of Suleiman's army, Ibrahim eventually fell from grace after an imprudence committed during a campaign against the Persian Safavid empire during the Ottoman–Safavid War (1532–55), when he awarded himself a title including the word "Sultan". Another conflict occurred when Ibrahim and his former mentor, İskender Çelebi, repeatedly clashed over military leadership and positions during the Safavid war. These incidents launched a series of events which culminated in his execution in 1536 by Suleiman's order. It is believed that Hurrem's influence contributed to Suleiman's decision. After three other grand viziers in eight years, Suleiman selected Hurrem's son-in-law, Damat Rüstem Pasha, husband of Mihrimah, to become the grand vizier. Scholars have wondered if Hurrem's alliance with Mihrimah Sultan and Rüstem Pasha helped secure the throne for one of Hurrem's sons.