Al-Hussain (radiyAllâhu ‘anhu) reaches
After an arduous journey of almost a month, his party reached
Meanwhle Kûfah was placed under heave surveillance by Ibn Ziyâd. When news of Hussain’s (radiyAllâhu ‘anhu) approach reached him, he dispatched a 4000 strong contingent, which was on its way to fight the Daylamites, to stop Hussain (radiyAllâhu ‘anhu). This contingent was put under the command of ‘Umar ibn Sa‘d. There can be little doubt that the Kûfans witnessed the departure of this force from Kûfah with their own eyes. This would be their last chance to honor the oaths of allegiance to Hussain (radiyAllâhu ‘anhu) which they had taken upon the hands of Muslim ibn ‘Aqîl. This was the final opportunity to rush to the side of the grandson of Rasûlullâh (grace, glory, blessings and peace be upon Him). It was after all their invitations and assurances of support that encouraged him (radiyAllâhu ‘anhu) to abandon the safety of Makkah for the precarious battlefields of
Al-Hussain (radiyAllâhu ‘anhu) is Martyred
And when the sun set on the 10th of Muharram, it was too late for the faithless Shî‘ah of Kûfah to make amends, for the sands of Karbalâ was stained red with the blood of Sayyidunâ Hussain and his seventy-one followers (radiyAllâhu ‘anhum).
Four years later the Shî‘ah of Kûfah attempted to make amends for their desertion of the family of Rasûlullâh (grace, glory, blessings and peace be upon Him). There emerged a group of Kûfans calling themselves the Tawwâbûn (Penitents) who made it their duty to wreak vengeance upon the killers of Hussain (radiyAllâhu ‘anhu). On their way to Syria in pursuit of Ibn Ziyâd they passed by Karbalâ, the site of Sayyidunâ Hussain' s grave (radiyAllâhu ‘anhu), where they raised a great hue and cry, and spent the night lamenting the tragedy which they allowed to happen four years earlier. Had they only displayed that same spirit of compassion for Hussain (radiyAllâhu ‘anhu) when he was so much in need of it the history of Islâm might have taken a different course.
The Sheites seek to hide their Treachery - 1
There have been attempts by certain writers to absolve the Shî‘ah from the crime of deserting Hussain (radiyAllâhu ‘anhu). Some find an excuse for them in Ibn Ziyâd’s blockade of Kûfah. S. H. M. Jafri writes in his book The Origins and Early Developments of Shi’ah Islam:
…it should be noted again that the blockade of all the roads coming into Kûfa and its vicinity made it almost impossible for the majority of those Shî‘îs of Kûfa who were in hiding, and also for those residing in other cities like Basra. 
This explanation of their desertion does not seem plausible when one considers the large number (18 000) of those who had taken the bay‘ah at the hands of Muslim ibn ‘Aqîl. Ibn Ziyâd, as we have seen, entered Kûfah with only 17 men. Even the force that he dispatched to engage the party of Sayyidunâ Hussain (radiyAllâhu ‘anhu) at Karbalâ consisted of only 4000 men. 
Furthermore, that force was not recruited specifically for Karbalâ; it was only passing through Kûfah on its way to fight the Daylamites. It is not at all credible to assume that Ibn Ziyâd was able to cow the Kûfans into submission with forces such as these, whom they outnumbered by far. It was rather their own treacherousness and fickleness that led them to abandon Sayyidunâ Hussain (radiyAllâhu ‘anhu). This can be clearly seen in the manner they deserted Muslim ibn ‘Aqîl.
There is also the tendency of claiming that those who deserted Sayyidunâ Hussain were not of the Shî‘ah. Jafri writes:
… of those who invited Hussain (radiyAllâhu ‘anhu) to Kûfa, and then those 18,000 who paid homage to his envoy Muslim b. ‘Aqîl, not all were Shî‘îs in the religious sense of the term, but were rather supporters of the house of ‘Alî (radiyAllâhu ‘anhu) for political reasons - a distinction which must be kept clearly in mind in order to understand the early history of Shî‘î Islam. 
Jafri’s motive in excluding the deserters of Sayyidunâ Hussain (radiyAllâhu ‘anhu) from the ranks of the “religious” (as opposed to the “political”) supporters of the house of Sayyidunâ ‘Alî (radiyAllâhu ‘anhu) is quite transparent. He is clearly embarrassed by the fact that it was the Shî‘ah themselves who abandoned their Imâm and his family after inviting him to lead them (radiyAllâhu ‘anhum) in revolt. What leads us to reject this distinction between “religious” and “political” supporters is the fact that Sayyidunâ Hussain (radiyAllâhu ‘anhu) himself, on more than one occasion, referred to the Kûfans as his Shî‘ah.