On the night of 9/10 December, Kler ordered the two battalions to close into within 1,000 yards of the Jamalpur defences to carry out detailed reconnaissance. Systematic air and artillery bombardment was kept up on the enemy defences and battalion headquarters in daytime on 10 December. To unnerve his troops completely, the last air sorties were asked to drop napalm bombs. Although these were dropped far from the target, they had the desired effect. The will to withstand a similar attack the next day began to break down.
As the same time, Mahmood was asked by Brig Qadr, Commander Pakistan Ad Hoc 93 Infantry Brigade Group, whether he could get his force to Dacca. He had appreciated the total Indian strength across the river as a weak battalion spread over 8,000 square yards and did not expect to encounter more than two companies along the road to Tangail. He told the commander confidently that he saw no problem and would break through the roadblock and take his troops back to Dacca. In discussing the battle with Kler later in Dacca, he said that being a staff college graduate he could not comprehend how the Indians could put across anything more than one weak battalion with no bridging or rafting equipment to do so. Kler told him that the only snag he did not take into consideration was that he had been only a student whereas Kler had taught at staff college. The second mistake Mahmood made was to try to soften up the likely roadblock localities with artillery fire, but this gave away his intentions of breaking out that night.
Throughout the night the Pakistanis reportedly came in wave after wave shouting warcries and the battle raged till 0430 hours on 11 December.
About 2350 hours on 10 December some Pakistani movement was heard along the Tangail road coming towards the forward company localities of I Maratha Light Infantry. The battalion held its fire till the Pakistani troops came within 20 yards of the depth company locality. Then a hail of machine-gun fire mowed down those who tried to escape. Throughout the night the Pakistanis reportedly came in wave after wave shouting warcries and the battle raged till 0430 hours on 11 December. To release pressure on 1 Maratha Light Infantry, Kler ordered 13 Guards and companies of 6 Sikh Light Infantry to close in on the fortress from the flanks and 13 Rajputana Rifles to cross the river. Throughout the battle, the affiliated artillery 66 Mountain Regiment gave close support by bringing down concentrations near the roadblocks and was a great help in beating off the attacks. Brar displayed good leadership by the cool and calm manner in which he conducted the battle.