Imam Hussein (A.S.) did not possess the necessary force that would enable him to win; he did not even rely on those who wrote to him from Kaufa. For he declared his revolution before he received their letters and delegates.
Al-Hijaz too did not give him enough support to be able to stand against the Ummayads. Therefore he decided to leave to Iraq for the sole reason of preventing any blood shedding in the Holy City of Mekkah.
Moreover, he knew that he was destined to die, yet he went on.
Why then did he insist; and why did he declare his revolution?
To answer this question, one should be aware of the following facts:
First: Yazied represented a real danger to the Islamic nation, for he was not a true Muslim. He was not properly educated with the teachings of Islam. And he used to drink alcohol, gamble, and commit all other sins according to historic sources. He said: Banu Hashim staged a play to obtain the Kingdom. Actually, there was neither any news (from Allah) nor any revelation. Such a man could not be entrusted with the affairs of the nation.
Nevertheless, the faithful forces, with Imam Hussein (A.S.) as their leader, had benefited a lot from these points of weakness in the personality of such an evil ruler.
In these circumstances it might not be strange to see many Muslim dignitaries trying to convince Imam Hussein (A.S.) to avoid the confrontation with Yazid, although they bore witness to the corruption of the Ummayads, and they also realized that it was the Imam's duty and right to face it... He was thus approached by Abdallah bin Umar bin Khattab and Abdallah bin Al-Zubair, as well as some of his family members.
These are some of the manifestations of the absence of the militant spirit among most Muslim leaders.
As for the common people, this negative spirit spread among them to a terrifying extent. The people of kaufa, for example, broke all their pledges promises and oaths, once they were subjected to the wave of terror led by Ibn Ziyad, as well as seducing them with promises of wealth and power.
These factors were among the main reasons that led to the announcement of the revolution. The Imam wanted to shake the dead consciences because he knew that there was no reason what speeches and talks to galvanize and mobilize the people and solidify their morals.
Second: The general level of the nation as a whole was below the required to stand up to the current of sweeping deviation. A tendency to treasure the pleasures of this world began to be visible in all sections of the nation, as a substitute to the spirit of sacrifice for the cause of Allah. And this enabled the opportunistic current to win and hold the positions of ruling and guidance.
Third: It was necessary that the nation should learn about the true Islamic conception of the Imamate; it's true role and its dimensions. The dangerous effects of undermining the Islamic conceptions which was played by the Ummayad rule was never emerging from the grassroot level, but rather from the high levels of leadership that monopolized all means of guidance.
Therefore, in accordance with the demands of the Islamic message, and the qualities that have to be available in a Muslim ruler, Imam Hussein (A.S.) had to explain these issues to the Muslim masses in every speech he made or any other opportunity he had:
"O people you have to be pious believers, and know the right. That is better for you. We the members of the family of Muhammad (Ahl ul-Bait) are more entitled to be the rulers than those who claim what is not rightfully theirs; those oppressors and tyrants".
With such roaring words the Imam Hussein(A.S.) revealed that the Ummayads who have deviated from the right Islamic path are not fit to be rulers, and explained to the nation the foundations of the course an Islamic traits that are embodied in the embodied in the Imam himself that qualify him to be Imam of the nation.
Thus, underlining the Islamic conception of the Imamate and revealing the falsehood of the Ummayad claims were among the fundamental reasons that made the Imam declare his revolution.
Fourth: The Islamic message offers no justification for the Muslim to relief him from performing his duties as a man who has obligations towards the message he believes in. Man in the Islamic society is not an independent individual but rather a person who is integrated in his society and who should perform his duties towards the Islamic message.
But to fulfil his commitments towards Allah's Shariah in enjoining the good and forbidding the evil meant that he had to follow the path of the revolution, because it was the only way that provided any hope for reform in his grandfather's (S.A.W) nation.
These are the main reasons that gave Imam Hussein (A.S.) and his companions the right to declare the victorious revolution, that immortalized Islam and inspired the coming generations to defend it and to hold fast in the Holy Wars of Jihad.