At the cumulative end of both Operation Trident and Python Karachi had suffered enormous losses. Sinking of PNS Khaibar, PNS Muhafiz and crippling of PNS Shahjahan and later damaging of PNS Dacca had significant impact on the operational events in the Arabian Sea. Besides naval ships several Karachi-bound merchant ships were sunk or damaged because of the Indian anti-ship missile assaults. Seeing the outcome of Trident and Python, Indian navy had figured the third missile attack, code named ‘Operation Triumph’ on 10 December 1971. However, PNS Hangor sank INS Khukri just a day before the launch of Triumph that changed almost everything in the Arabian Sea. Indian navy was on a roll in December 1971. Indian naval planners were bent upon avenging Operation Somnath that Pakistan naval ships undertook in the 1965 War routing the town of Dwarka and destroying key naval installations there. Long before the practical use of sea-based land attack missile, Pakistan Navy conducted a real ‘from the sea’ operation that had caught Indians totally off guard. Presence of PNS Ghazi made sure that no Indian surface ship had dared pursuing Pakistani surface flotilla that had carried out Dwarka bombardment. It was an unpredictable operation that still lives in the annals of Indian military history. Learning the lessons of the 1965 War was one of the cornerstones of Indian naval strategy that manifested in the 1971 War. Indian navy knew the limitations of Pakistan navy’s air surveillance and less guarded Karachi port complex. Newly acquired Soviet missile boats armed with Styx SS-N-2B anti-ship missile were timely and innovatively utilized in a bid to ‘settle’ score for Dwarka bombing. Indian navy’s Operation Trident, executed on the night of 4/5 December resulted in loss of PN ships Khaibar and Muhafiz and over 290 lives. Whereas Operation Python, conducted on the night of 8/9 December, damaged PNS Dacca beyond repairs. Both Trident and Python resulted in loss of fuel storage at Kemari, which, however, was recovered swiftly. Pakistan Navy inherently aligned itself with the doctrine of ‘active response’ given the fact its geographic contiguity with a numerically superior and a militarily provocative neighbor. Indian state-sponsored and state-supervised support to separatists in the East Pakistan compelled Pakistani military to prepare for the war that most certainly was in the offing. Pakistan Navy’s operational estimates were suggestive of ‘forward deployment’ of naval assets in a quick timeframe by the start of November 1971. PNS Hangor and PNS Ghazi were deployed to keep Indian capital ships under watch at Bombay and Vishakhapatnam respectively. PNS Hangor sailed Karachi by 26 November to be around Bombay harbour for operational tasks. Once in the area, Hangor had an eventful deployment. There were several operational defects and technical inhibitors, which otherwise would have meant return of the vessel back to base. Captain and the crew of the boat remained poised, hopeful and resilient to face the turbulences and came out clean. On one such occasion, as Vice Admiral (then-Commander) Ahmed Tasnim, the Commanding Officer (CO) of Hangor, would later recall, was the closing of an Indian naval destroyer while the submarine was at surface near Diu Head. The submarine appeared, to the destroyer, just like a fishing boat due to exceptional lateral thinking of the captain, who was able to disguise a military ship into a non-combatant vessel. Indian ship approached Hangor and later changed course. The crew rectified the defect and then dived for the next patrol spot. The war hadn’t been declared as of 2/3 December as Hangor didn’t have orders to engage the adversarial ships. While in position off Bombay, Hangor did pick up trail of several ships on a course towards Karachi. CO Hangor evaluated it to be a surface group probably destined to undertake operations off Karachi harbour. The submarine attempted to warn of the impending attack by breaking the radio silence. Indians picked up the transmission and two ASW frigates, INS Khukri and INS Kirpan were tasked to search, locate and neutralize a probable Pakistani submarine in the area. In the meantime, the Operation Trident had been undertaken followed by Python by morning of 9 December. Hide and seek between Hangor and Khukri-Kirpan group continued, one evading the other. By 4 December, Hangor was given a clear message to attack and destroy any Indian ship that the submarine might detect. Cdr Tasnim and his team prepared the torpedoes and got the men ready for the assault against the Indian naval ships. Daphnes had a reliable fire control system of that time, and with superior passive sensors it was highly likely to discriminate between a small and large naval vessel. On 9 December around 1900, Hangor detected and classified two Indian destroyer/ frigate sized ships coming together within the submarine attack area. An hour later, Cdr Tasnim dived to about 40-45 m and shot a ‘down-the-throat’ torpedo at one of the two ships, which later turned out to be INS Kirpan. It was a well calculated and deliberate attack, but somehow the torpedo missed the target and alerted Kirpan. CO Kirpan assessed a subsurface attack and maneuvered to flee the scene leaving Khukri to its fate. INS Khukri, after having learnt about a submarine attack on Kirpan, moved towards the submarine to attack. Meanwhile, Hangor reoriented its firing priorities and focused on the second Indian ship. As Khukri closed, Hangor was ready with its torpedoes to attack. This time the shot was hard to miss. The second torpedo fired by Hangor ripped Khukri to its pieces and within two minutes the ship sank with 194 crew members including officers and sailors. Kirpan moved back to the scene of devastation first to attack Hangor and later rescue survivors but found itself as a target of third Hangor torpedo. Kirpan was almost crippled as the torpedo hit the ship fairly well but did not sink it as it had already started torpedo evasive steering. Later Cdr Tasnim moved Hangor to the scene of sinking in a bid to rescue survivors, but unfortunately there was none. What happened after the sinking of Khukri was the largest submarine hunt to this day! Almost entire Indian navy’s Western Fleet was out to search and destroy Hangor. Almost 200 depth charges were indiscriminately dropped in a hope to sink Hangor where it was or force it to surface. Hangor remained dived for about 7-8 days after the attack. Indian submarine hunt was fruitless and as well as significantly frustrated. Superior tactical mastery and ‘out-of-the-box’ application of strategy ensured Hangor remained harmless. Cdr Tasnim was able to lure Indians into believing where Hangor wasn’t present. Hangor returned harbour safely on 18 December. Indian navy celebrates 4 December as ‘navy day’ while erroneously labelling Operation Trident as the ‘decisive naval operation’, which in accordance with any agreeable military definition of a ‘decisive action’ is untrue. Had Trident been decisive there wouldn’t have been the necessity of Python and later Triumph. On the contrary, Hangor’s act squarely fits the defining markers of a ‘decisive military operation’, which significantly altered Indian approach to the Arabian Sea. Indian navy quickly cancelled the ‘planned’ Operation Triumph and did not conduct any further naval operations in the area off Pakistani coast. Legacy of Hangor endured in Pakistan navy. Hangor Day is celebrated on 9 December in Pakistan. Pakistan navy is acquiring eight submarines (four will be built in China and four in Pakistan) which are named after Hangor submarine as ‘Hangor Class’ submarines. Fifth submarine of Hangor class will be commissioned as PNS Tasnim to honour the valiant captain who sank an Indian ship and then survived the post attack onslaught.