Submarine Operations

The Sinking of INS Khukri

With the outmoded surface fleet almost neutralised by the missile threat, the burden of the Pakistan Navy’s entire offensive effort hinged on the small but effective submarine force.

Pakistan Navy submarine Hangor slipped in the early hours of 22 November, 1971 for a patrol off the Indian Kathiawar coast under the command of Commander Ahmad Tasnim, SJ. On this very day the Indian Army had launched a large scale invasion of East Pakistan, which was to hurl the nation into a full scale war within a fortnight. But the submarine commander and her crew, could hardly have been aware of this development when she quietly slid past Manora break­water on her way to the allocated area for a reconnaissance patrol. On 23 November, when a state of emergency was declared by Pakistan, Hangor was off Porbandar close to the Indian coast and on the morning of 24 November her sensors picked up considerable activity by military and civil aircraft extending up to 100 miles from the Indian coast. On 1 December she received orders directing her to shift to a patrol area off Bombay vacated by PN Submarine Mangro on comple­tion of her patrol.

Hangor was on the surface on the night of 2 December when at 2340 a large formation of ships was detected on her radar on an easterly bearing about 35 miles away. Such abnormal detection ranges are frequently obtained in this area in the winter months due to anomalous propagation of radio waves, a phenomenon which results from the trapping of radio waves in ducts formed due to temperature inversions in the atmosphere. Hangor closed this formation to a range of 26 miles at 0049 on 3 December, when she dived to a depth of 40 metres and tracked the ships on her sonar till the early hours of the morning. A quick sweep by her radar at periscope depth revealed that the formation consisted of 6 escorts screening a main body of four ships. This was undoubtedly the Western Fleet comprising the cruiser INS Mysore with supporting auxiliaries and her escorts which had sailed from Bombay on 2 December.

At this time, though an all out war was raging in East Pakistan, hostilities had not broken out in the West. Hangor could not hangor_muhafiz_sattack these ships as she did not have clearance to do so. It was not until 0820 on the morning of 4 December that Hangor learnt about the outbreak of hostilities through C-in-C’s message received on the submarine broadcast. Frustration and disappointment at missing their prey by such a narrow margin was great for the Commanding Officer and the crew. But Hangor’s endeavours were not entirely in vain. Location of the Indian Fleet at this crucial time was by itself a significant accomplishment. In this case, however, her vigilance also contrib­uted towards the cancellation of a missile attack which this force was scheduled to launch at Karachi on the night of 5 December. Suspect­ing detection by the submarine, the Indian Fleet split and moved so far south that it was no longer in a position to execute its attack plan.

Hangor continued her patrol. Occasionally she closed Bombay harbour and detected some warships operating in waters too shallow for the submarine to make an approach and launch its torpedoes. At other times her limited submerged speed, the main handicap of conventional submarines prevented interception of good targets. The officers and men of Hangor were not deterred by these disappointments.

In an effort to locate the evasive enemy, Hangor extended her patrol northwards to investigate some radio transmissions that she had intercepted on her sensors. In the early hours of the morning of 9 December, when she was off the Kathiawar coast, two contacts were picked up on her passive sonar on a north-easterly bearing. They were easily identified as warships by their sonar transmissions; radar indicated a range of 6 to 8 miles. A pursuit of the enemy began.

It must be understood that though the submarine enjoys the advantage of stealth, restrictions on its operations are many. It has a much lower speed when submerged compared to surface ships. Therefore, an attack is only feasible if the submarine is in a sector ahead of its target. Higher submerged speed to intercept its target means lowering of battery capacity, which must be preserved to evade the enemy after attack. The motive power of a submarine in the submerged state is dependent an batteries which must be frequently charged by coming up on the surface or snorkelling. A submarine is extremely vulnerable when moving at high speed in shallow waters. Not only can it be easily detected due to higher noise level, but chances of its evading the enemy are sharply reduced, if detected, due to lack of manoeuvring space in the vertical plane. These factors were carefully considered and weighed by the submarine com­mander and his control team as the boat manoeuvred to take up a position ahead of the patrolling frigates.

When the first attempt to intercept the ships failed, the submarine began snorkelling to gain speed. Hangor, however, failed to attract the attention of the ships and contact was lost as the range increased. By the evening of 9 December, she was able to make out the pattern of their movement by tracking them with the aid of her sensors. The ships were carrying out a rectangular anti-submarine search.

Forecasting their movement along this search pattern the subma­rine succeeded by 1900 in taking up a tactically advantageous position on the path of the patrolling frigates. The range of the ships, which were moving at a speed of 12 knots, began to close. The crucial moment which the submarine had patiently worked for since the early hours of the morning had arrived. Hangor was finally in a position to launch an attack.

At 1915 she went to action stations. Fifteen minutes later she came up to periscope depth, but could see nothing in the dark night when the range of the ships indicated by her periscope radar was only 9800 metres. The ships were completely darkened. The Command­ing Officer decided to go down to 55 metres depth and make a sonar approach for the final phase of the attack. Unaware of the submarines presence, the frigates continued on their track. At 1957, Hangor fired a down-the-throat shot with a homing torpedo at the northerly ship from a depth of 40 metres. The torpedo was tracked but no explosion was heard. This was not the time to brood over the situation. The control team sprang into action and fired a second torpedo. After five tense minutes a tremendous explosion was heard at 2019 hours. The torpedo had found its mark. The other enemy frigate came straight for the submarine. Hangor fired a third torpedo and turned away at maximum speed. A distant explosion was heard subsequently.

Moving west towards deeper waters, where she would be less vulnerable, the submarine passed very dose to the scene of action and heard distinctly the noise of explosions emanating from the burning wreck. Later she came up to periscope depth and took a last look. In the dark, nothing could be seen except a faint glow on the horizon near the scene of action.

In an extremely vulnerable position in enemy controlled shallow waters where no help could reach her, the task that lay ahead of Hangor was to evade her pursuers in the hunt that followed – the first signs of which came when a number of underwater explosions were heard just about half an hour after the attack. For the next four days Hangor braved the might of the Western fleet. All their anti-submarine assets – frigates, Seaking helicopters and Alize aircraft were thrown into the chase that followed. A hunterkiller (anti-submarine) operation fully supported by IAF reconnaissance aircraft based ashore in the area, was put into effect.

The problem of making good its escape by a submarine after an attack is in many respects more challenging and complicated than the attack itself. For all the contending demands produced by a variety of submarine limitations need to be reconciled in a hostile environment in which the position of the submarine is known to the enemy. Higher underwater speeds increase the rate of discharge of her batteries, which requires more snorkelling; and in this mode she is exposed to detection by the enemy. Lower submerged speed means more time in hostile waters, increasing the possibility of detection.

The first priority of Hangor after the attack was to get into deeper waters and put as much distance between her and the position from which the torpedoes were fired, the datum (reference point) for the search by enemy units. Having successfully done that, she began her journey back home. For four days and nights she was harassed by the enemy. The dimensions of the enemy anti-submarine effort can be gauged from the fact that about 150 underwater projectiles were fired in this period. Only on one occasion were the explosions close enough to shake the submarine.

The Commanding Officer was naturally keen to pass the information of this successful attack to Naval Headquarters. The submarine had to come up as it cannot transmit radio messages while submerged. She took the risk of being fixed by enemy direction finding stations ashore while transmitting the message. Enemy aircraft were over­head soon after the message was sent. Intense air activity throughout the day forced the submarine to run silent and run deep, reducing her speed of advance to 1.5 knots.

There were, of course, many close calls during the passage back to Karachi. The Indian Navy called off the futile hunt on the evening of 13 December. There were claims by same of their units to have sunk the submarine, but she arrived unharmed at Karachi on 18 December.

hangor_sIn this spectacular action which took place about 30 miles south of Diu off the Indian Kathiawar coast, INS Khukri, the ship of the Squadron Commander of the 14th Frigate Squadron, was sunk within two minutes after receiving a hit in the magazine where explosives were stowed. 18 officers and 176 sailors including the Commanding Officer, who deliberately stayed back on the sinking ship, lost their lives. This came as a shattering blow to the Indian Navy, deflating in one stroke the exuberance generated by highly exaggerated success stories of the missile attacks at ships off Karachi.

If Hangor’s action demonstrated our tactical superiority in sub­surface warfare, the strategic impact was even more significant. The Indian Navy cancelled “Operation Triumph”, the third missile attack, which was to be launched on 10 December. Involvement of the Western Fleet for tour days in the hunt for the submarine took the pressure off our coast. The morale of our officers and men soared.

After the war, even the critical BBC commentators praised Pakistan’s naval effort. Considering the shape and size and age of the ships at its command, they said, the Pakistan Navy had acquitted itself well against the Indian Navy.

Commodore Rai in his hook ‘A Nation and Its Navy At War’ has ended with these words, “India will have to play its role in the Indian Ocean accordingly. The Indian Navy cannot ever say, ‘Ring off main engines. Revert to normal notice for steam’ It will have to lift its head in the Indian ocean and keep boilers banked if not steaming.” This is perhaps a warning.

In a sense we had same warnings of the loss of East Pakistan. In Pak-American Relations edited by K. Arif an extract is given of Intelligence Report No. 7894 of the Office of Intelligence Research and Analysis of the Department of State, 5 December, 1958.

‘Only under a democratic system would East Pakistan, with its greater population, appear to be able to match the greater military and bureaucratic weight of West Pakistan. However, the prospects of prolonged suppression of political freedom under military domination would intensify the risk of such an increase in tension and discontent in East Pakistan as perhaps to jeopardize the unity of the two wings of the country.’

Earlier, at the end of December 1952, ISI sent a priority signal to the Services Headquarters asking for detailed reactions of service personnel to the Basic Principles Committee report. Deputy Director Naval Intelligence (Commander SM Ahsan) had replied:

a. The creation of Committee of Ulema to veto the decisions taken in the House of People on religious matters, gives excess of powers to Ulema over the rights of elected representatives of the people. This gives an impression of Pakistan as being a Theocratic State.

b. To recommend that the head of the state should be a Muslim will unnecessarily create suspicions in minds of the minorities in Pakistan. The choice to select the head of the state should be left entirely to the people, to select without prejudice to caste, colour and creed.

c. It is maintained by same officers that a single House elected on population basis should have been envisaged, and we should cease to think in terms of Bengalis and Punjabis etc. The parity between West & East Pakistan will ultimately result in the division of Pakistan into two different groups, therefore, it is the very negation of one people, one country and one culture.

A stranger than fiction fact is that this document was contained in a file numbered – 1971!