Rahman organised an infantry unit gathering all Bengali soldiers from military and EPR units in Chittagong. He designated it Sector No. 1 with its HQ in Sabroom. A few weeks later he was transferred to Teldhala where he organised and created Sector 11. All sectors were restructured officially under Bangladesh Forces as the sector in the Chittagong and Hill Tracts area, under Colonel M. A. G. Osmani, the Supreme Commander of Bangladesh Forces, of the Provisional Government of Bangladesh which had its headquarters on Theatre Road, Calcutta in India. On 30 July 1971 Rahman was appointed the commander of the first conventional brigade of the Bangladesh Forces, which was named "Z Force", after the first initial of his name. His brigade consisted of 1st, 3rd and 8th East Bengali regiments, enabling Rahman to launch major attacks on Pakistani forces. With the Z Force, Rahman "acquired a reputation for icy bravery" according to "The New York Times", and was awarded the Bir Uttom, the second-highest military honour (and the highest for living officers) by the Government of Bangladesh.