Muawiyah was successful in deceitfully gaining the absolute power he had aspired for. He was not interested in the functions of preaching piety or theology. He was interested in expanding his sphere of influence in the territories already conquered by the Muslims, and was actively engaged in further conquests to the north and north west of Syria. In utter violation of the terms of the Treaty with the Imam, Muawiyah decided to name his son Yazid to succeed him after his death. He knew that Yazid lacked all qualifications to be a caliph for the Muslims and to represent the Holy Prophet of Islam. He also knew that the Imam, being a true representative of the Prophet, would oppose the nomination of his son. Consequently, he decided to eliminate the opposition.
Muawiyah solicited the services of Marwa'n bin Hakam, a son-in-law of the third Caliph, who was the governor of Madinah at that time. With a promise for a reward, Marwan approached one of the wives of the Imam, Ju'da binte al-Ash'ath bin Qais to poison the Imam. He was successful, and the Imam died as a result of this plot.
Before he died Imam Hasan, in accordance with the Will of Allah, named his brother, Husain to be the next Imam. He expressed his wish to his brother to bury his body near to the grave of his grandfather, the Prophet of Islam. This caused an armed opposition by the governor of Madinah. Under a shower of arrows, the jenazh (funeral procession) of Imam Hasan had to withdraw and be diverted to Jannatul-Baqi', the general graveyard of Madinah, where he was buried.