We Sank the Khukri

Just thought I should share the story of this less known but amazing feat of naval combat performed by the Pakistan Navy during the 1971 Indo-Pak war. This is an excerpt taken from the book ’Sentinels of the Sea – The Pakistan Navy’ by Rear Admiral R. Kadri.

We Sank the Khukri
By
Rear Admiral R. Kadri, SJ (Retd.)

INS Khukri

November 20, 1971 was a holiday and so was 21 November – two whole days “free” during the difficult days of turmoil in East Pakistan. It was Eid-al-Azha, time for sacrificial offering of animals, of family get-togethers and of feasting and sharing of joys. However, 1971 was not to be a year for such celebrations for us. The Indians had decided that 1971 was their year of the “opportunity of the century” and they were not about to miss the opportunity.

It was already apparent to any thinking person keeping track of the unfolding events that with each passing day, he day of decision was drawing nearer. The Indians had to intervene in East Pakistan during that winter or miss the “opportunity of the century” forever.

PN Submarine Ghazi had been dispatched only a few days earlier to the Bay of Bengal for operations in that distant area, should the need arise. The mission assigned was difficult and dangerous but the submarine had sailed out in a blaze of glory with the battle cries of Allah-Ho-Akbar little knowing that this was to be its last mission.

I was at that time the Electrical Officer of PN submarine Hangor and therefore before going home for two days Eid holidays had made sure, as is the practice, that everything was ready in case the submarine was required to proceed to sea at short notice. Except for attending the congregational Eid prayers, I had decided to stay at home. There was no visiting relatives or friends, only a quiet day at home, knowing that the Indians always preferred days or events of National or religious importance to launch their attacks.

Eid day passed off quietly, but on the evening of second day of Eid my front gate bell rang. Thinking it might be a visitor, I went to open the front gate, but on seeing a naval police patrolman standing there, realization at once dawned that the time of waiting and uncertainty was over and that time had finally come for the submarine Hangor to put to sea.

This was confirmed by the patrolman. I therefore quickly changed into uniform, picked up the small handbag which was already packed for such an eventuality and with a quick goodbye to wife and children sped away at breakneck speed towards the Submarine Base – praying all the way to be granted enough time to enable our submarine to put to sea before hostilities commenced in the Western theatre of war also.

On reaching the Submarine Base, I found that those submariners who lived nearer or had been contacted earlier had already reported for duty, while others like me were just arriving. The fact that not a single officer or sailor wasted a single second in reporting for duty, and every single one of them reported promptly, showed that without being told, every submariner had the same thought in mind and had kept himself ready for this eventuality.

As each member of Hangor’s crew arrived on board, he knew exactly what had to be done in terms of final preparations, and set about doing it. Family, friends and festival were all forgotten – only the mission and the task at hand mattered. It was a good team, disciplined and well trained and needed no guidance.

After the sailing-orders had been received, all the submarines, with their identification numbers painted out slipped silently from their berths one by one, as their departure times came, to proceed separately to their respective patrol areas. From now on hey would be on their own, without contact with the outside world except to periodically receive, and that too only when possible, radioed instructions from Naval Headquarters. They themselves could not contact the outside world and, in order not to compromise their location, would have to maintain complete radio silence, except to pass an extremely important message.

PNS Hangor sets sails for its patrol with the identification number painted off.

Once the submarines were in their patrol areas, all contacts if classified as warships or submarines, were to be considered hostile. From now on life would be a constant effort to stay one jump ahead of the enemy. Every emission and every noise, be it electro-magnetic, sonic or ultra-sonic would have to be checked, measured, plotted, analysed and evaluated. On this would depend whether you were the attacker or the attacked in this deadly game.

Once Hangor had cleared the Manora breakwater, on the way to its patrol area, ships company automatically fell into its usual three watch system, with one watch on duty and two watches “off”. This would now be the constant routine except when “action stations” were closed up or during other emergencies when everybody would be closed up at his allocated station, depending on the type of emergency.


I found myself in the “off” watch at this stage and therefore, after checking once again that everything was shipshape in my department, I turned in to take some rest before my own watch which would be in the middle of the night.

While lying in my bunk, I could not help reflecting back on that cold, grey and gloomy early morning of November 1969 at Brest, France, when I happened to be standing on the gates of a submarine pen in which Hangor had been docked. I still remember the deadly appearance its sleek, black hull presented with the sharp lines of its vertical rudders, the horizontal planes and stabilizers sticking out like the fins of shark, and saying to myself: “God help those who fall prey to this deadly submarine”. Well! Hangor, the shark, was now loose at last, fully armed and hunting for real prey. No more exercises. All e training was behind. It was now the real thing – kill or be killed. In submarine warfare there isn’t much room for any other choice once the battle is joined, especially when an anti-submarine force itself is one of the targets.

Hangor reached it’s patrol area without encountering any enemy units, though a lot of air activity was seen and frantic communication traffic intercepted. Until 2 December Hangor operated in various areas, as ordered by Naval Headquarters, sometimes encountering small vessels such as ferries and dhows and some merchant ships. Indian warships generally remained out of the area, except for some close inshore patrolling by their small frigates and patrol craft in shallow waters out of reach of the submarine.

Late in the afternoon of 2 December Hangor’s sensors picked up a number of radar emissions from the direction of Bombay harbour. These emissions were analysed and were correctly identified as transmissions of radars fitted on certain Indian warships. It was also correctly appreciated, taking various factors into account, that this presaged imminent sailing out of the Indian Western Fleet. A little latter a sudden jump in the strength of the radar emissions was again correctly appreciated to indicate that the Indian fleet had indeed sailed out of harbour. Hangor, thereafter, kept close watch on it, tracking it be radar emissions as well as the propeller H.E. (Hydrophone Effect) of ships.

At about 2340, when the strength of the radar emissions indicated that the Indian fleet was within our radar range, the radar mast was raised and a radar sweep was taken from periscope depth. This radar sweep clearly painted ten enemy contacts. On the radar screen a clear picture could be seen of four ships of the main body in the centre of the formation being screened by six units around it.

Hangor having estimated the enemy’s course and speed found itself ahead of the approaching enemy, and set course to intercept. Finally, with “action stations” closed up and with all torpedoes ready for launch, Hangor managed to penetrate the anti-submarine screen and ended up between the main-body and its protective screen, in an ideal position to attack both and could have played havoc with the Indian Fleet. All the crew’s preparations and training had been for this moment. Had the rules of engagement permitted, we could have fired torpedoes at the enemy units as fast as we could line up the sight on each target. But the enemy was just about to be granted a reprieve, for all submarines had sailed out with strict orders not to engage the enemy unless fired upon first or till these orders were cancelled by Naval Headquarters. There had been no change in these orders, and therefore all that Hangor could do was to pass under the enemy ships and then break radio silence to make an enemy contact report to Naval Headquarters. It was one of the most frustrating experience that a submariner can go through. It was even more frustrating to learn later on that hostilities had commenced in the Western theatre on 3 December, within a few hours of the submarine’s encounter with the Indian fleet.

The Indian Fleet had a close call and Hangor missed a golden opportunity but, after restrictions on engaging enemy units were lifted, its crew became even more determined to ensure that no enemy units in its patrol area escaped unscathed. However, the submarine’s tribulations were not yet over and one of the cooling pumps on board broke down. Without repairs to this pump it would not be possible to continue its war patrol. But repairs to this pump involved shutting down the main air conditioning plant of the submarine and lifting and removing its compressor motor to gain access to the defective pump.

Repairs to the pump itself were not much of a problem but removal of the air conditioning plant compressor motor was a different matter entirely, posing many serious problems.

In a submarine, owing to lack of space, machinery is closely packed so that access to machines fitted close to the hull is only possible after removal of the intervening machinery in a specific sequence. Also, due to lack of space, certain heavier machines can only be lifted and moved after cutting the “soft” deck plates above the machine and then re-welding the plates back after the repairs are completed. The AC compressor motor was one such machine.

Even during peacetime in harbour with all dockyard facilities available, the task would have taken approximately a week to complete. We now had to choose either to return to harbour for repairs – which everyone on board realized would effectively put the submarine out of the war or attempts to effect repairs at sea in enemy waters with none of the dockyard facilities at hand. In case it was decided to effect repairs at sea, there was a further question of whether to carry out repairs with the submarine completely submerged or partly surfaced. Detection by enemy aircraft in the middle of repairs would necessitate crash dive by the submarine, with the possibility of the detached heavy compressor motor causing further damage to material and men. Also, the repairs had to be completed in hours rather than days or weeks.

Hangor’s crew were a determined lot. They did not want to sit out the war in the safety of Karachi harbour and had a tradition of accepting challenges. It was therefore decided to carry out the repairs at sea. Carrying out repairs at sea with the submarine completely submerged and the air conditioning plant shut down was not possible as not only the heat inside the submarine would be unbearable for the crew, but also the rise in humidity would lead to problems in the very important electronic equipment due to condensation of water vapour on sensitive circuits. It was, therefore, decided to take a risk and work with the submarine partially surfaced. A sharp lookout was to be maintained for enemy aircraft and surface units and at the first sign of the enemy, the submarine was to dive.

Once the decision was taken, work was commenced in right earnest and continued without break. The spirit of the crew had to be seen to be believed. Everybody from the commanding officer to the junior most sailor was involved in the work in one way or the other. If the requirement was to keep a look out for the enemy, the sharpest eyes and ears were constantly at it. If any thing was required by the repair team, it was promptly provided if available, if not, it was improvised. Those who could not contribute by their technical knowledge contributed with their muscle power, and those who could not even contribute in this way, maintained a constant flow of nourishment in the form of tea and water to those working cramped in tight corners, soaked in the oily bilge water. There was no distinction by branch or seniority, everyone contributed in whatever way he could.

The impossible had finally became possible and, even under the most hazardous conditions faced by Hangor, the repairs were completed in under 48 hours. Everybody heaved a sigh of relief when the submarine was able to submerge completely once again, with the repaired pump working satisfactorily and the air conditioning plant back in operation. Like a true shark, Hangor was back on the hunt once again, having effected repairs in the enemy’s own backyard.

Hangor’s crew had worked hard and made many sacrifices. While at sea none of them had any idea of what their near and dear ones faced back on shore. Everyone of them had responded to the call to duty without hesitation. Even he Eid holidays had been spent in the waiting. The cool pleasant days of November and December, when officers and men would normally be thinking of annual leave to go north, were spent in this deadly game of hide and seek. Surely it was an act of God that our sacrifices did not go unrewarded.

The reward came in the form of two distant contacts early on the morning of 9 December 1971. Analysis of the contacts had already established that they were two warships equipped with radars and sonars. But their speed and course were such that the much slower submarine could not catch up with them. They were, however, tracked and by the afternoon the analysis of their behaviour indicated that they were doing a rectangular anti-submarine search. The two contacts were thus appreciated to be two anti-submarine frigates engaged in SAU (Search and Attack Unit) operations.

It was therefore decided to wait for the ships at a selected point on their search pattern, rather than chasing them all over the place. This strategy paid off as the two contacts started closing, late in the evening. Course and speed of the submarine was adjusted to ensure being in a position to attack at a time of our own choosing.

By 1900 Hangor was waiting on the estimated rack of the targets. Everyone on board already knew what was happening and there was an air of expectancy everywhere. The targets were still behaving as anticipated and range was steadily closing with both frigates still operating their sonars. “Action Stations” was therefore sounded at 1915. The “shark” had bared it’s teeth, and it’s moment of truth had come. Next few minutes would permanently seal the fate of one of the two frigates.

Though the enemy was operating sonar, Hangor had not been detected and therefore still enjoyed the advantage of surprise. She knew too well that failure to hit the enemy at first attempt would shift the balance of advantage completely in favour of the two anti-submarine frigates. Hangor had to hit the enemy first, and hit hard at the first attempt.

Already the factor of shallow depth (60-65 meters) in the area was working in favour of the enemy as the submarine did not have much room to maneuver in the vertical plane to avoid enemy’s depth charges, should that be necessary.

Outside, it was dark, the sunset already having taken place. It was, therefore, decided to go deep and to carry out a blind (Sonar only) approach and attack. The attack team now concentrated on tracking the two targets as they gradually came within firing range. (After the war, these two targets were identified as INS Kirpan and INS Khukri. Thus, with the benefit of hindsight we can henceforth refer to all three participants in the unfolding drama by their proper names.)

After having obtained a perfect solution Hangor commenced the attack at 1957 by firing one homing torpedo, “down the throat” at the more northerly target, which was INS Kirpan. The torpedo ran true and it was tracked on sonar all the way as it acquired “lock on” to the target and passed under it (as it was supposed to do). However, the newly acquired torpedoes, whose test facilities had not yet been set up, failed to explode and kept going. Until the time that the torpedo was fired neither of the two frigates had any inkling of being under attack. However, the moment the torpedo passed under INS Kirpan, she suddenly woke up, realized she was under attack and turned away at maximum speed. Hangor had struck first, but had failed to hit hard. The new torpedo had let it down.

The advantage had now shifted completely in favour of the enemy. If the enemy had kept their cool, it is difficult to say what would have been the final outcome. Perhaps, this article would not have been written in such detail. But one thing is sure – the fate of INS Khukri would still have been what it was.

As Kirpan turned away and ran, Khukri, which was to its south, now knowing the direction from which the torpedo had come, increased speed and came straight for an attack on Hangor.

It was now Hangor’s turn to keep it’s cool – and this, the submarine did well. As Khukri came in for attack, Hangor’s attack team calmly shifted target to Khukri, obtained a quick solution and fired the second torpedo at it. This quick shot was mostly meant to spoil he attack by Khukri, however loss of nerve by Khukri’s Commanding Officer on hearing the oncoming torpedo, made him try to turn away from it. This greatly helped to “pull” the torpedo towards the frigate. As soon as the torpedo acquired “lock on” it went straight for the target, passed under it and when it was directly under the keel it exploded, breaking the keel of INS Khukri which sank in a matter of two minutes, with all hands on board. There were no survivors. There was simply no time for the myth of the “CO nonchalantly lighting a cigarette as the ship sank under him” to be enacted.

The sinking of Khukri had now made the balance of advantage even between Hangor and Kirpan and the action had not yet finished.

Seeing its sister ship sink in such a short time must have been a nerve shattering experience for the Kirpan’s Commanding Officer, for he came charging in for an emergency attack, fired off a pattern of depth charges, hoping to scare Hangor away into breaking off its attack. But when he found that the Hangor was not intimidated and instead had fired the third torpedo at Kirpan, he broke off the attack just as quickly and ran “hell for leather” in panic trying to outrun the torpedo locked on to the frigates tail. That was the last seen (actually heard) of her.

Hangor, the shark, had struck first. It had struck hard in the second attempt, and in the third attempt the surviving enemy frigate had been left worrying about the “torpedo locked on to its tail”.

What followed this action was a massive anti-submarine effort by the Indian Navy, in the form of Operation Falcon to hunt down and kill just one submarine, PNS/M Hangor. The operation was launched shortly after the sinking of the Khukri, on the night of 9 December and continued for four days till the night of 13 December.

During these four days, the Indian Navy utilized all available anti-submarine ships, Alize (Specialized anti-submarine naval aircraft), shore-based surveillance aircraft and Sea King anti-submarine helicopters in HUK Groups (Hunter-Killer Groups) and combed an area extending from the point southwest of Diu Head, where Khukri was sunk, right upto a point just short of PAF’s air-strike range from Karachi.

Details of Operation Falcon are given in the book ‘War in The Indian Ocean’ written by Vice Admiral (Retd) Roy, IN.

In fact, indirectly Hangor was responsible for another loss to the Indian Navy, for according to Admiral Roy, during Operation Falcon, the Indian Navy also lost an Alize anti-submarine aircraft at sea with all three of its crew.

What Vice Admiral (Retd) Roy has not mentioned is the number of anti-submarine charges fired, on what the HUK groups thought was Hangor. In the submarine itself 24 salvoes (each of three charges) on 10 December and 12 salvoes on 12 December were registered. The latter depth charging took place after Indian Navy’s shore stations had taken cross bearings on Hangor’s radio message to Naval Headquarters regarding the action.

Throughout these four days Hangor remained completely aware of the huge effort underway (though the details of Operation Falcon as such were known only after the war) and it is a measure of Hangor’s efficiency that in spite of leaving the action area with a highly depleted battery, and with such a massive hunt for her in progress, she managed not only to recharge her batteries but was able to successfully lay a false trail for the HUK groups to follow. How successful the false trail was, can be judged from the fact that of the more than 36 salvoes fired, only two slightly shook the submarine. Most being far away and could just be heard on sonar. In spite of this, the Indians claimed to have sunk the Hangor a number of times between 9 and 13 December.

By now, the submarine had been at sea for over 21 days and, though the body odours of the crew were getting stronger and the unshaven hair on their chins longer, their morale was sky high. They had just been through the ultimate test as submariners, both collectively as well as individually. They all knew in their own hearts how they had stood the test, and they were satisfied.

PNS Hangor returns from her successful war patrol.


Credit to Usman from Pakdef for typing the whole thing.

—————————————————————————————————-

– Interestingly this was the first incident of a submarine sinking or damaging a vessel of any kind since the end of WWII. There has been only two other incidents like this since then. One was when HMS Conqueror sank the Argentinian Navy ship ARA General Belgrano during the Falklands War and the other happened recently when a North Korean Yeono class midget submarine torpedoed and sank ROKS Cheonan.

-The actual sonar recordings of this engagement, which were recorded by Hangor’s sensors, can be heard at Pakistan Maritime Museum, Karachi. One can hear the initial ‘pings’ of Kirpan’s sonar, its engine noise and then the torpedo leaving PNS Hangor’s torpedo tube, moments later INS Khukri’s sonar with much sharper sonar ‘pings’ and engine noise and another torpedo leaving Hangor’s torpedo tube can be heard, and lastly a huge explosion can be heard as the torpedo explodes beneath the INS Khukri.

-PNS Hangor is now a museum ship and can be visited at the the Pakistan Maritime Museum, Karachi.

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