The Vijay Diwas is observed every year on December 16 to commemorate the victory of the Indian forces over Pakistan in 1971.
Indo-Pakistani War of 1971 took place in East Pakistan from 3 December 1971 until 16 December 1971, when Pakistan surrendered in Dhaka.
The conflict took place during the Bangladesh Liberation War. During Operation Chengiz Khan, Pakistan launched a preemptive air attack on 11 Indian air stations, resulting in the conflict.
During East Pakistan's war for independence, this action sparked hostilities between Pakistan and India, escalating the conflict between both sides.
Indian forces gained a decisive advantage after the Pakistani military's Eastern Command signed the surrender instrument 13 days after the war began.
In this way, East Pakistan became Bangladesh. India declared 16th December as Vijay Diwas.