To The Better World
They prevented him from meeting with his followers as they prevented ulama and scholars from contacting with him to take from the fountains of his sciences. And this, as I think, was the worst distress the imam suffered. They tried more than one time to assassinate him but Allah protected him from their plots.
There were some reasons that made the Abbasids bear a grudge against Imam Abu Muhammad (AS). Here are some of them:
First, the Abbasids feared from the Awaited Imam whom the Prophet (AS) had brought good news about and told that he would be the greatest reformer that mankind had never seen like him throughout all stages of history.
The Prophet (AS) told that the Awaited Imam (AS) would spread political, social justice allover the world, would do away with all kinds of injustice and oppression, and defeat all tyrants and oppressive powers in the world. He would do away with polytheism and atheism, and raise the banner of faith and truth. He would revive the annulled laws of Allah. Therefore, the Abbasids tried to kill Imam Abu Muhammad (AS) to be sure he would not leave offspring. Imam Abu Muhammad said about that, ‘They claimed that they wanted to kill me in order to cut off my offspring, but Allah falsified their saying, and praise be to Allah.’
Second, the Abbasids bore envy towards Imam Abu Muhammad (AS) for his popularity and the great respect that all classes of society showed him, whereas the authority was in the hand of the Abbasids who received nothing of respect or honoring from people. therefore, they plotted day and night to do away with him.
Third, the Alawids rose in many revolts against the Abbasid rule since its beginning aiming at achieving the political justice of Islam and applying its economical and social programs in life. Those revolts were supported by great masses of people in the different Muslim communities that harmed the dignity of the rule and shook its throne and were about to overthrow it.
Those revolts filled the hearts of the Abbasids with hatred and grudge against the Alawids, and so they ordered their policemen to chase every Alawid. It was naturally that Imam Abu Muhammad (AS) suffered the bitterest distresses from the Abbasids because he was the master and chief of the Alawids and the imam of Muslim at that time.
 Kifayat al-Athar.
Taken from : The Life Of Imam Al-Hasan Al-Askari Study And Analysis By: Baqir Shareef al-Qurashi Translation by: Abdullah al-Shahin