Imam  Hasan   Mujtaba, upon whom be peace, was   the second   Imam. He and his brother Imam Husayn were the two sons of Amir al-Mu'minin 'Ali and Hadrat Fatimah, the daughter of the Prophet. Many times the Prophet had said, "Hasan and Husayn are my children." Because of these same words 'Ali would say to his other children, "You are my children and Hasan and Husayn are the children of the Prophet." Imam Hasan was born in the year 3 AH, in Medina and shared in the life of the Prophet for somewhat over seven years, growing up during that time under his loving care. After the death of the Prophet which was no more than three, or according to some, six months earlier than the death of Hadrat Fatimah, Hasan was placed directly under the care of his noble father. After the death of his father, through Divine Command and according to the will of his father, Imam Hasan became Imam; he also occupied the outward function of caliph for about six months, during which time he administered the affairs of the Muslims.

During that time Mu'awiyah, who was a bitter enemy of 'Ali and his family and had fought for years with the ambition of capturing the caliphate, first on the pretext of avenging the death of the third caliph and finally with an open claim to the caliphate, marched his army to Iraq, the seat of Imam Hasan's caliphate. War ensued during which Mu'awiyah gradually subverted the generals and commanders of Imam Hasan' s army with large sums of money and deceiving promises until the army rebelled against Imam Hasan. Finally, the Imam was forced to make peace and to yield the caliphate to Mu'awiyah, provided it would again return to Imam Hasan after Mu'awiyah's death and the Imam's Household and partisans would be protected in every way. In this way Mu'awiyah captured the Islamic caliphate and entered Iraq. In a public speech he officially made null and void all the peace conditions and in every way possible placed the severest pressure upon the members of the Household of the Prophet and the Shi'ah.