Al-Fat~h bin Khaqan...
Al-Fat~h bin Khaqan, the prime minister of al-Mutawakkil, preferred Imam al-Hasan al-Askari (a.s.) to all eminent scholars and ulama and acknowledged that no one had the virtues and qualities that the imam (a.s.) had at that time. It was natural that the nation, with all classes, regarded and glorified Imam Abu Muhammad (a.s.) for they saw his guidance, piety, righteousness, asceticism, loyalty to the truth, and devotedness to Allah.
They were certain that he was the caliph of Allah in the earth and the only representative of his grandfather the great Prophet (a.s.). In addition to that, Imam al-Hasan al-Askari (a.s.) undertook the fatal issues of the Islamic nation and defended the rights of Muslims. He criticized the rulers of his time for wronging people and disregarding their rights. Therefore, the nation glorified him and acknowledged his necessary leadership.
The Abbasid kings became displeased when they saw and heard that the masses glorified Imam al-Hasan al-Askari (a.s.), and that great numbers of Muslims believed in his imamate and thought that he was worthier of the caliphate than the Abbasids who had no quality that might make them fit for the Islamic caliphate. Spite against the imam (a.s.) filled the hearts of the Abbasid rulers who took severe procedures against him.
They imposed economical blockade against him, and put him under house arrest in Samarra’. They surrounded him with policemen and detectives to watch even his breaths. They subjected every one who contacted with him to severe punishments. This was-as I think-the reason that made just few narrators narrate traditions from him, and so not many maxims, literatures, and religious rulings were transmitted from him.
There was another very sensitive reason that led the Abbasids to watch Imam al-Hasan al-Askari (a.s.) strictly. It was that Imam al-Hasan al-Askari (a.s.) was the father of Imam Muhammad al-Mahdi (a.s.) the awaited savior and reformer who would fill the world with justice, and would destroy oppressors and oppression.
The Prophet (a.s) and his guardians gave good tidings, and told the nation that this savior would spread political, social justice in the earth, and all Muslims of different trends believed in that. Therefore, the Abbasids were afraid of that and thought that he would remove their rule and authority. They spread spies on Imam al-Hasan al-Askari (a.s.) to know his son.