The Hasan–Mu'awiya treaty was a political peace treaty signed in 661 between Caliph Hasan ibn Ali and Mu'awiya I () to bring the First Fitna (656–661) to a close. Under this treaty, Hasan ceded the caliphate to Mu'awiya on the condition that the latter should rule in compliance with the Quran and the , a council should appoint his successor, and Hasan's supporters would receive amnesty. Upon accession, Mu'awiya publicly recanted his earlier promises, while Hasan retired from politics in Medina, and was later killed in 670 by poisoning. Mu'awiya is commonly viewed as the instigator in the murder of Hasan, which removed an obstacle to the succession of his son Yazid (), whose nomination violated the treaty with Hasan. Throughout his reign, Mu'awiya also prosecuted notable partisans of Hasan and his father Ali. Historical background After Ali's assassination in 661, his eldest son Hasan was acknowledged caliph in Kufa. Having been at war with Ali, Syria's governor Mu'awiya () did not recognize the caliphate of Hasan, and led an army into Kufa, while pressing Hasan for abdication in his letters. In response, Hasan sent a vanguard under Ubayd Allah ibn al-Abbas to Maskin to block Mu'awiya's advance until he arrived with the main army. Meanwhile, Hasan faced a mutiny in his camp, likely ignited by Mu'awiya's spies, and was severely wounded in a failed assassination attempt by the Kharijites, a faction opposed to both Ali and Mu'awiya. This attack demoralized Hasan's army and led to widespread desertions. Ubayd Allah and most of his troops also defected after Mu'awiya bribed him. When Hasan learned about this, he reproached the Iraqi nobles for their fickle-mindedness. Peace treaty Mu'awiya now sent envoys to propose that Hasan abdicate in his favor to spare Muslim blood. In return, Mu'awiya was ready to designate Hasan as his successor, grant him safety, and offer him a large financial settlement. Hasan accepted the overture in principle and sent his representative(s) to Mu'awiya in Maskin, who sent them back to Hasan with carte blanche, inviting him to dictate whatever he wanted. Hasan wrote that he would surrender the Muslim rule to Mu'awiya if he would comply with the Quran and , his successor would be appointed by a council (shura), the people would remain safe, and Hasan's supporters would receive amnesty. His letter was witnessed by two representatives, who carried it to Mu'awiya. Hasan thus renounced the caliphate