Pakistan’s Naval headquarters was based at the historic and strategic port of Karachi here almost their entire fleet was concentrated. Karachi not only represented the area of maximum strategic importance, but also was also critical for Pakistan’s external trade and maritime interests, meaning that a blockade would be disastrous for Pakistan’s economy. For these reasons, the port received some of the best defence Pakistan had to offer as well as cover from strike aircraft based at two airfields in the proximity.
To counter India’s involvement in Bangla Desh freedome struggle, on December 3rd, the Pakistan Air Force (PAF) flew sorties against 11 airfields in India, under Operation Chengiz Khan in an attempt to reduce the numerical superiority held by the Indian military. Indian Air Force (IAF) retaliated later in the evening, starting 1971 war. On 4th December Indian Navy launched Operation Trident and caused heavy damages to Karachi port without any damage to any Indian ship.
On the 8th December night, under operation Python, the missile boat INS Vinash escorted by the frigates INS Talwar and INS Trishul set course for Karachi at high speed. En route, electronic emissions were detected on a Pakistan Naval frequency, which were being monitored. It was appreciated that a vessel with a powerful transmitter was reporting the presence of the force to Maritime headquarters Karachi. The vessel was soon sighted and Talwar opened fire, blasting the communication craft to pieces. At 2300 hrs, the group arrived off Karachi and detected a group of ships on radar. When around 12 miles off Karachi, after some careful calculation, Vinash fired all her 4 missiles at her contacts, 3 of which were ships and the other a coastal target.
Python was another successful operation by the Indian Navy. The Pakistani fuel reserves for the sector were destroyed. India had established complete control over the oil route from the Persian Gulf to Pakistani ports. Shipping traffic to and from Karachi, Pakistan’s only major port at that time, ceased. The Pakistani Navy’s main ships were either destroyed or forced to remain in port. A partial naval blockade was imposed by the Indian Navy on the port of Karachi.