When in 40 A.H. 'Ali b. Abi Talib had been murdered in Kufa, his son, al‑Hasan succeeded him to the caliphate. 'Ali had collected a force of 40,000 men to march on Syria in an attempt to put down Mu'awiya1.
The latter on the pretext of avenging the death of his uncle 'Uthman had been steadily increasing his power and authority at 'Ali's expense. When 'Ali was killed, confusion rapidly developed among the forces which he had assembled. It soon became apparent to al‑Hasan that the situation had reached the point where any continuation of hostilities against Mu'awiya would result in catastrophic defeat. In order to avoid this and the useless bloodshed that such a defeat would involve, al‑Hasan came to terms with Mu'awiya.
A version of the settlement made between al‑Hasan and Mu'awiya has been preserved by Ibn A'tham2.
These are (the terms) on which al‑Hasan b.'Ali b. Abi Talib settled with Mu'awiya b. Abi Sufyan. The latter would make peace with the former provided that he handed over to him authority for ruling the believers on condition that:
1. He (Mu'awiya) governed them according to the Book of God and the sunna of His Prophet, Muhammad, and the practice established by the righteous Caliphs (sirat al‑khulafa 'al‑salihin)3;
2. Mu'awiya was not to make a bequest (of the caliphate) to anyone after him. Rather the matter should be (settled by) a shura (deliberative council) of the Muslims after him;
3. The people (al‑nas) would be guaranteed security wherever they were in the land of God, Syria, Iraq, Tihama or Hijaz;
4. The followers of 'Ali and his shi’a were guaranteed security with regard to their persons, property, women and children;
5. Accordingly Mu'awiya would take up the covenant and compact of God (ahd Allah wa‑mithaquh); what God barred from any of His creatures would be compensated by what He gave of His own accord;
6. He (Mu'awiya) would not oppress al‑Hasan, nor his brother al‑Husayn nor any of the family of the Prophet (ahl bait al‑nabi) with any evil (gha’ila) either secret or public, nor cause any of them to be afraid anywhere.
Then follow the names of witnesses to the document.
The document, if genuine presents several points of interest. It demonstrates that succession to political authority was to be decided by the Muslims and was not to lie in the hands of Mu'awiya. Although many Shi'i would oppose the idea of a shura to decide the next political leader instead of the office going automatically to the leading member of ahl al‑bait, it was the sort of compromise that al‑Hasan would have to have made. After all he himself was to pledge allegiance to Mu'awiya as the political ruler. The second important point is that Mu'awiya guaranteed the security of all 'Ali's supporters. Some of these had been involved in the death of 'Uthman and as Mu'awiya's pretext for the war was to avenge the death of 'Uthman, the treaty reveals that Mu'awiya's real interest had been the acquisition of power. The sixth clause is an undertaking by Mu'awiya not to harm any member of the Prophet's family. The public cursing of 'Ali which continued after the treaty seems to violate the condition, particularly when the ancient Arab view of cursing is taken into consideration.
Al‑Tabari does not include this treaty. However he does include a story from al‑Zuhri of how Mu'awiya had sent al‑Hasan a blank sheet with his own signature at the bottom, but at the same time al‑Hasan had sent a sheet including his own terms, which were much less than Mu'awiya had expected. When al‑Hasan received Mu'awiya's letter he doubled his demands but Mu'awiya, as he had the original terms of al‑Hasan, refused to accept al‑Hasan's second terms4.
The only things mentioned by al‑Tabari consist of funds in the Kufan treasury and security for al‑Hasan and his family5. The accounts seem to indicate at this point a strong Umaiyad bias, but at least they give evidence for the existence of a version of the treaty which was not adhered to by Mu'awiya, and probably was the actual treaty.
Al‑lmama wa‑l‑siyasa attributed to Ibn Qutaiba includes only one condition that "The (terms) on which he, al‑Hasan, made peace with him were that the Imamate should belong to Mu'awiya for as long as he was alive, but when he died, authority should belong to al‑Hasan."6
This can hardly have been the full treaty and it looks like a gloss on the 2nd condition in Ibn A'tham's version. It seems likely that al‑Hasan believed that the Imamate would revert to his family if the items of that condition were adhered to.
There seems to be fairly strong evidence that although al‑Hasan gave the oath of allegiance to Mu'awiya, al‑Husayn did not. According to Ibn A'tham al‑Hasan dissuaded Mu'awiya from attempting to force al‑Husayn to pledge allegiance to him7.