Three Indian corps were involved in the liberation of East Pakistan. They were supported by nearly three brigades of Mukti Bahini fighting alongside them, and many more who were fighting irregularly. That was far superior to the Pakistani army of three divisions. The Indians quickly overran the country, selectively engaging or bypassing heavily defended strongholds. Pakistani forces were unable to effectively counter the Indian attack, as they had been deployed in small units around the border to counter the guerrilla attacks by the Mukti Bahini. Unable to defend Dacca, the Pakistanis surrendered on 16 December 1971.