Hassan (RA) was the grandson of our beloved Prophet (PBUH) and was a very peaceful person.
Hassan ibn Ali (RA) was the eldest son of Fatima (RA) and the first grandson of the Holy Prophet (PBUH). The Holy Prophet (PBUH) loved Hassan and his brother Hussain a lot and spent a lot of time with his grandsons. Hassan Ibn Ali (RA) spent almost 7 years in the love and care of the Prophet (PBUH).
Life in the shadow of Ali (RA)
The death of the Holy Prophet (PBUH) led to a lot of confusion concerning the succession as a Caliph. Hassan (RA) was a great help to his father Ali when he became the Caliph and played an active role in assisting Ali (RA). He participated in many battles such as that of Basra, Siffin and Nahrawan alongside Ali (RA) and showcased strength and valor on the battlefield as a soldier and a leader.
Hassan as a Leader
The death of Ali (RA) meant that a new caliph had to be appointed. Being the eldest son of Ali (RA), Hassan (RA) was the first choice of the people and he accepted his responsibilities and duties as a Caliph fully. The Muslims of Kufa pledged allegiance to Hassan without any disagreements.
This however did not play well with Muawiyah who was already fighting Ali (RA) for Caliphate. Muawiyah started to gather an army to fight this young new Caliph while also attempting to negotiate with Hassan via letters in which he demanded that Hassan (RA) renounce his claim to Caliphate and step down. Since Hassan refused to accept this demand, an army of sixty thousand men came forth to fight against Hassan’s (RA) army of forty thousand men near a place called Sabat.
Hassan (RA) gave a sermon to gather his followers and to unite them against a common enemy Muawiyah. The sermon was misunderstood by many who thought that Hassan (RA) was going to surrender and so many rebelled against him and attacked the new Caliph. The armies still met however and fought a few inconclusive fights. Hassan (RA) could see that this war would only lead to a loss of men and nothing fruitful will come out of it. Hence he decided to negotiate with Muawiyah who too wanted to avoid unnecessary skirmishes. The two parties came to an agreement on the conditions put forth by Hassan (RA) and the fighting stopped. Prophet (PBUH) is known to have prophesied about this earlier saying: “It is this grandson of mine, on whose hands the two great armies from amongst the Muslims will stop fighting.”
However, the peace treaty within the two parties did not last very long as Muawiyah did not uphold his part of the deal.
Retirement to Madina
Even when Hassan (RA) relinquished his rights as a caliph and passed them on to Muawiyah a lot of disagreements arose. In addition to the abuse and taunts slung at Hassan by Muawiyah, he also had to withstand and endure the resentment of his followers who did not want someone like Muawiyah as their ruler. Hassan, however, had made this decision only in the greater interests of the religion and his people, who failed to understand why such an action was necessary. Hassan is reported to have said: “If Muawiyah was the rightful successor to the Caliphate, he has received it and if I had that right, I, too, have passed it on to him; so the matter ends there.” This statement was a testament to the prophecy of Prophet Muhammad (PBUH) about Hassan bringing peace between two warring factions of Muslims.
Hassan’s Martyrdom
Muawiyah always saw Hassan as a big threat to this position as a leader and hence he plotted to kill him. He instigated one of Hassan’s wives to poison him and she did so by mixing poison in honey. Muawiyah had promised great things to the wife who poisoned Hassan, and once the deed was done, he retracted his words and broke all promises he had made to her.
Hassan suffered at the hands of his wife who poisoned him and passed away a few days later after falling sick. Just before his death, he entrusted the affairs of leadership to his brother Hussain and made him the guardian of his family and the people. Hassan was buried in Jannat-ul-Baqi as per his wish.
CREDIT: Omam Khalid
https://www.islamicfinder.org/iqra/the-life-of-hassan-ibn-ali-grandson-of-prophet-muhammad/