Headed by Colonel MuhammadAtaur Gani Osmani, a retired Pakistani army officer of Bangladesh, this band was raised as Mujib's action arm and security force before assuming the character of a conventional Guerrilla force.After the declaration of Independence, the Pakistani Militarysought to quel them, but increasing number of Bengali soldiers defected to the underground "Bangladesh army."These Bengali units slowly merged into the Mukti Bahini and bolstered their weapnry.
On April, 1971, Colonel(later general)M.A.G.Osmani assumed the command of armed forces Teliapara, Sylet Headquarters. Osmani was made the commander-in-chief of Bangladesh Armed forces on 17 April, 1971.Serious inititiave for organising the Bangla Desh Liberation army was taken betweeen 11-17 July. In a meeting of the sector commanders in Kolkata , four important resolutions were taken in consideration of strategic aspects of the war, existing problems, and future course of resistance.