Mitro Bahini order of battle

The Indian Army had no standby force ready in 1971 with the specific task of attacking East Pakistan, one of the many reasons why India did not immediately intervene after Pakistan launched Operation Searchlight in March 1971. Indian Army's Eastern Command was tasked with defending the northern and eastern borders and fighting the insurgencies in Nagaland, Mizoram and Naxalites in West Bengal at that time.

Source: Wikipedia — Mitro Bahini order of battle (CC BY-SA 4.0)