INS Khukri, was a Type IV ASW Frigate belonging to the 14 Squadron of the Western Fleet of the Indian Navy during the 1971 War with Pakistan. She was the only Indian sea vessel that was destroyed by the enemy, and sank off the coast of Diu, on the night of December 9, 1971, taking down with her about 178 sailors and 18 officers including Khukri's Captain - Mahendra Nath Mullah.
The sinking of INS Khukri continues to haunt the minds of military strategists and planners even today. Because, this was the only instance where the otherwise highly effective planning and tactics of the Indian Navy like those used to sink the Ghazi and for the Karachi attacks, did not come into play.
I have tried to put together, a few critical factors that led to this incident which was a huge irreparable loss:
1. Pakistan Navy's strength lay in her new "Daphne Class" submarines, three in number, acquired recently from France (and funded by the United States). The strength of the submarines was in her sensors and armament which was regarded as 'superior to anything in the Indian Navy's inventory'
Soon after the war started, certain Pakistani communication intercepted by the Indians established two facts - a)that these communications were submarine transmissions and b)that these were originating from an area around Diu, which was the main assembly areas for Indian warships to be deployed for missile attacks. Naturally this caused a lot of concern to the Indian Navy.
The 14th squadron, consisting of 'Khurki, Kirpan and 'Kuthar' has sailed along with the western fleet on December 2, 1971. Soon after the Kuthar encountered a boiler burst, and had to return to Bombay for repairs. She was towed back by the Kirpan, with Khukri acting as escort. During this journey, the Khurki reported encountering a submarine, and attacking it. While this fact was never established, it further strengthened suspicion that Pakistani submarines were in the vicinity. Consequently, a "Hunter-Killer" operation was ordered the main objective being to seek and destroy and Pakistani vessels.
The first mistake - was deploying the 14 squadron for this operation. These old frigates were pitted against modern submarines which had a sonar range twice that of the Khurki and Kirpan. Additionally with the Kuthar damaged the squadron strength was sub-optimal.
Khukri and Kirpan sailed nevertheless, to take up the difficult task of a 'hunter -killer' operation in an area 50 miles by 55 miles off the coast of Diu.
PNS Hangor the submarine responsible for the sinking of the Khukri, lay patiently in wait, near Diu. Hangor picked up 2 contacts on her sonar at extreme range , in the early hours of the morning of December 9 when she was off the Kathiawar coast. When they were identified as warships from their sonar transmissions, the submarine began pursuit. By the evening on December 9, she was able to make out the pattern of movement of the two Indian ships, by tracking them with her advanced sensors and concluded that the ships were carrying out a rectangular anti-submarine search. By forecasting their movement, the submarine succeeded by 7 pm, in taking up a tactically advantageous position in the path of the patrolling frigates.
The second mistake - was the linear path followed by the frigates covering a rather small area instead of a 'zig zag' course. The range of the frigates that were moving at a speed of 12 knots was now closing and the Hangor prepared for the attack. The Khukri was still not aware of the submarine's presence and continued doing slow speed on a steady course on a narrow weave which was a flagrant violation of the anti-submarine doctrine.
The third mistake - was that the Khukri continued to do 10-12 knots instead of the normal 15 knots required not only to seek and destroy the enemy but also for evasion.The reason for this was the attachment of a special device by the Khukri's electrical officer, Lt. V.K Jain, to the Type 14's 170/174 sonar to slightly increase it's detection range. This new device developed with assistance from BARC, was approved by Admiral Kohli to be embarked in the Khukri
The fourth mistake - the two frigates were being supported by 'Sea King' helicopters which were anti submarine weapon platforms with torpedoes and highly effective sonars. They were therefore powerful deterrents to the Pakistani submarines. As long as they were there in the vicinity of the Khukri and the Kirpan, PNS Hangor would never have dared to surface or to attack.
The Sea Kings had departed from the scene of action between 5 pm and 6 pm, because their reliefs failed to arrive, and they were running low of fuel. The helicopters left, and the frigates were assured that the relief choppers would arrive within an hour.
The relief helicopters failed to arrive, and this gave Hangor the opportunity she was looking for.
Hangor fired a down-the-throat shot with a homing torpedo at the Northerly ship (Kirpan) at about 8 pm. The torpedo however misfired and Kirpan detected the torpedo going past her and fired her mortars, which after a few salvoes being fired, became non-operational. Without losing time, Hangor turned towards the Khukri. Hangor fired a second torpedo, which exploded under the Khukri's oil tanks. A few minutes later Kirpan returned for an attack in a course that brought her in line with the submarine. Hangor fired a third torpedo and immediately turned away and exited at maximum speed
According to the Pakistani version, the torpedo exploded near the stern of the Kirpan, badly damaging it and putting her out of action though in reality, Kirpan was not scratched and returned for rescue operations along with the vessel, INS Katchal. The Indian version maintains that both the torpedoes hit the Khukri.
Kirpan was faced with a dilemma -should she immediately lower her boats and rescue the survivors of the Khukri which would leave her vulnerable to the submarine or should she leave the area, repair her defective mortars and return with an additional ship to commence the rescue and hunting operations. Under the circumstances, Kirpan made the wise choice of doing the latter.
This action however generated some discussions on the ethics of such tactics for quite some time in Indian navy circles.
INS Khukri sank soon after.
Whether the 'mistakes' listed above were indeed mistakes - only military strategists can comment on. They certainly explain the circumstances and conditions that led to the sinking of INS Khukri - the only Indian ship to be destroyed during the war.
1. 'The Sinking of INS Khukri - Survivors' Stories' by Maj Gen Ian Cardozo
2. 'Loss of INS Khukri' by B. Harry (Bharat Rakshak.com)