After gaining independence, Pakistan had realized in order to endure freedom, it ought to have a strategic ability to turn down malicious designs of its enemy. Pakistan well perceived the importance of its coastal defence and to have a hand in sea, Pakistan Navy was brought into service. Historically seen, the main purpose of establishing navies is to exert influence beyond their shores entails with additional responsibility to further strategic stability and peace at sea. Despite remained vigilant to defend its sea borders, Pakistan Navy, competing with the challenges of technology and globalization, has constantly been engaged in contributing its share at regional and international maritime realm to comply by the international obligations for collaboration. Pakistan Navy in spite of numerically less in size, underscores high standards of professionalism. In 1971 war, Pakistan Navy conducted successful operations, meant for strategic deterrence and gave a befitting reply to anti-Pakistan forces, a similarity of which is hard to find in the domain of naval warfare. On 9th December 1971, the UK build Indian Anti-Submarine frigate INS KHUKRI was sunk and INS KIRPAN was badly damaged by the Pakistani submarine PNS HANGOR. The significance of this encounter increases manifold when viewed in retrospect that it was only the first occasion after world War-II, that a war ship was sunk by a conventional submarine in a live encounter at sea. It is important to realize that the HANGOR-KHUKRI action did not developed overnight and the events in 1971 were shaping for such actions due to crisis in East Pakistan. Consequently, Pakistan Navy submarine HANGOR sailed for a patrol off the Indian Kathiawar coast. PNS HANGOR reached its patrol area after successfully completing the difficult transit under the heavy enemy air activity and commenced her patrol. However, on 9 December 1971, when the submarine was off the Kathiawar coast; two contacts were picked up. They were identified as Indian warships by its sonar transmissions and were at a radar range of 6 to 8 miles. The two contacts were appreciated to be two anti-submarine frigates (INS KHUKRI and INS KIRPAN) engaged in Search and Attack Unit operations. HANGOR was waiting on the estimated track of the targets and “Action Stations” was therefore sounded that the “shark” had bared its teeth and its moment of reality had arrived. Although the enemy was operating sonar, HANGOR was not detected and therefore still enjoyed the element of surprise. The conditions were not favorable for conducive submarine operations due to shallow depth in the area and the enemy surface fleet was in advantageous position due to limited maneuverability of submarine. Nevertheless, HANGOR continued her approach and after obtaining a good firing solution; she commenced the attack by firing one torpedo at one of the ship. The torpedo ran and was passed under the warship and failed to explode. The enemy’s warship crew suddenly woke up realizing that they were under attack. HANGOR crew calmly shifted target to INS KHUKRI, obtained a quick solution and fired the second torpedo at it. This quick shot was an aim to spoil the attack by KHUKRI. The torpedo went straight for the target and exploded under the keel of INS KHUKRI. In this spectacular action, INS KHUKRI was sunk within two minutes after receiving a hit. 18 officers and 176 sailors including the Commanding Officer lost their lives. This came as a shattering blow to the Indian Navy, deflating in one stroke the exuberance generated by highly embroidered success stories of the missile attacks at PN ships off Karachi. To sum up, 9th December known as ‘HANGOR Day’ is being celebrated every year in order to pay tribute to the brave war veterans who struck terror in the hearts of the enemy by sinking the Indian Navy Frigate INS KHUKRI and crippling INS KIRPAN during the 1971 war.