It is celebrated to commemorate the state's liberation from Portuguese rule in 1961.
Goa had been under Portuguese rule for roughly 450 years since 1510.
After Portugal became part of the US-led Western military alliance NATO (North Atlantic Treaty Organisation) in 1949, Goa too became part of the anti-Soviet alliance by extension.
Operation Vijay was launched to liberate the three Portuguese territories: Goa, Daman and Diu.
It was supposedly the first tri-service operation of the Indian armed forces.