ভূমিকা
Shiavault - a Vault of Shia Islamic Books A Shi'ite Encyclopedia (chapter 5) Did Imam Al-husain (as) Know He Would Be Killed? A sunni brother mentioned: al-Husain (RA) was truthful in his detrmination to change the munkar, but he was adviced by the likes of Ibn Abbas and Ibn Umar that he was overoptimistic with the people of Iraq and their help. Husain, being a human who is not ma3soom like the prophets, excersised his Ijtihad.
Based on what is even reported by the Sunnis, Imam Husain knew that he will be killed in Ashura in Karbala, and yet he went forward. Not only Imam Husain, but also all the Prophets of God knew about the detail of this catastrophe. From Adam, to Noah, to Moses, to Zakariyya, to Yahya (John), to Muhammad, all cried for Imam Husain (AS) and remembered him on the day of Ashura.
Imam Husain, before he leaves Medina, saw the Messenger of Allah in dream who told him: "Verily Allah willed to see you martyred. Verily Allah willed to see your family captives" He knew that he will be killed where and how. There was no error in his part or what you called overestimation of the people of Iraq. A person who goes to a battle which has an uncertain ending, never takes his family, women, and children with him, and never put their lives in to jeopardy.
But Imam Husain did all that, knowing all the tragic events which will happen to them from setting their tents on fire (by the soldiers of Yazid) to plundering them and moving them from town to town. But he took with him women and children because they were supposed to deliver a message to the people of each town and to wake them up from their deep sleep.
No doubt that the event of Karbala was a turning point in the destiny of the religion of Islam, by which the religion was immuned form annihilation. Individuals, however, are not immune from going astray. But the blast in Karbala and its inspiring effects on the hearts of people never let Islam to be eradicated.
========= Another brother mentioned that if one knows that by going to certain place, he would be certainly killed, the going to that place is considered to be suicide, and as such, how could Imam al-Husain go toward Karbala if he knew that he would be killed? The above question is interesting. Imam al-Husain knew where and how he will be killed and who will kill him. This was the case for the other Imams of Ahlul-Bayt as well.
Even Sunnis narrated that the Prophet (PBUH&HF) told Imam Ali who kills him and when will he be killed.