Why Weren't Iranians Present in Karbala?

Iranians were unable to join Imam Hussein's army on the day of Ashura in 61 AH, but afterwards they stood alongside those who bore the flag of the House of Muhammad (PBUH). Their movement began with Mukhtar's support; later, the army of the black-clad soldiers, sent by Abu Muslim Khurasani towards Kufa, camped outside the city to enter on the day of Ashura in 132 AH and dismantle the Umayyad caliphate.