September 17 is observed as Hyderabad Liberation Day. It marks the historical date associated with the integration of the former princely state of Hyderabad into the Indian Union in 1948, following the military operation known as Operation Polo (also referred to as Police Action).
After India’s independence on 15 August 1947, the Nizam of Hyderabad, Mir Osman Ali Khan, sought to keep the large princely state independent rather than acceding to India. Prolonged negotiations failed, and reports of unrest and activities by the Razakars (a private militia) heightened concerns. On 13 September 1948, Indian forces under Major General J.N. Chaudhuri launched Operation Polo.
The operation lasted about five days. By 17 September 1948, Indian troops had advanced significantly, and the Nizam announced a ceasefire. The formal surrender of Hyderabad State Forces took place shortly thereafter, and the state was integrated into the Indian Union. The territory of the former Hyderabad State later became part of present-day Telangana, as well as portions of Maharashtra and Karnataka.
The Government of India has officially decided to commemorate 17 September every year as Hyderabad Liberation Day. A gazette notification issued by the Ministry of Home Affairs states that the day is observed to remember the martyrs who contributed to the integration of Hyderabad and to foster patriotism among the youth.