PNS Ghazi (S-130), formerly USS Diablo (SS-479), was a WWII submarine of the US Navy and later the Pakistani navy.
(Top: USS Diablo at sea during WWII. Bottom: The modified ex-USS Diablo in service with Pakistan as PNS Ghazi.)
(The bridge windshield of PNS Ghazi which was recovered by the Indian navy after they sunk the submarine.)
USS Diablo (SS-479) was a WWII Tench class submarine commissioned on 31 March 1945. A highly successful design, the Tench class measured 311’8″x27’4″x15’3″, had a crew of 78, and had a maximum diving depth of 400′. The Tench class had 10 torpedo tubes (6 forward, 4 aft) and could carry 24 torpedoes or mines. As designed, there was also a 5″ deck gun, two 20mm AA guns, and two machine guns. USS Diablo was in the Pacific en route to her first combat patrol when WWII ended.
As one of the newest submarines, USS Diablo was retained in the much-reduced peacetime submarine force, after transferring to the Atlantic fleet. During the late 1940s, the obsolete WWII guns were removed.
(USS Diablo in the Cape Cod Canal in 1950. By this time the deck guns had all been removed, but the submarine was otherwise still in WWII form.)
By the 1960s USS Diablo was falling behind the technology curve. In 1962 the submarine was redesignated as a research submarine (AGSS) but retained full combat potential and would have used it in time of war.
Fleet Snorkel Conversion
The Fleet Snorkel program came about when Congress refused to fund any more GUPPY I/II conversions of WWII-era submarines. Using “creative accounting” the US Navy pooled leftover GUPPY funds with regular upkeep budgets to provide a very limited upgrade for some additional WWII submarines. The Fleet Snorkel Conversion (officially designated SCB-47A) involved replacing the WWII conning tower with a tall, streamlined structure housing a new snorkel. New sonars were installed, as was a new air conditioning system and upgraded electrical plant. Some legacy items, such as magazines for the long-gone deck guns, were removed as was the old auxiliary diesel.
Unlike the GUPPY rebuilds the Fleet Snorkel submarines retained their WWII-design batteries and hull form, and got few additional electronics. As such, their underwater speed, range on batteries, and general effectiveness were significantly less than a GUPPY. None the less the project was a good way to get additional use out of old WWII-veteran submarines.
(USS Diablo in 1964, after the Fleet Snorkel Conversion and just before the submarine transferred to Pakistan. This photo gives a good view of the plexiglass bridge windshield which was later recovered off the wreck.)
USS Diablo underwent the conversion in 1963. As modified, USS Diablo displaced 1,570t surfaced and 2,414t submerged. The refitted submarine could make 20kts surfaced, 12kts snorkeling with the diesels, or 8 ¾kts submerged on battery power. The underwater endurance on battery power remained limited; 97NM at 2kts or 48 hours maximum. USS Diablo now had a crew of 76 (9 officers and 68 enlisted men). The submarine carried the SS-2 radar with an average range of 21NM, the AN/BLR-6 ESM system, and AN/BQR-2 sonar with a range of 4 NM.
The armament of USS Diablo in postwar American (and later, Pakistani) service remained the WWII-era Mk14 torpedo. The Mk14 was the main US Navy submarine torpedo of WWII. It had a range of 2 ¼NM at 46kts or 4 ½NM at 30kts, and had a 507 lbs TNT warhead. This was an unguided, straight-running torpedo inferior to the post-WWII homing designs. None the less, because of the huge quantity built, it remained in frontline US Navy use through the Korean War and in second-line service into the 1970s. The Mk14 was always the torpedo type included with exported American WWII-veteran submarines.
(The WWII-era Mk14 which was heavily exported after the war and used in the US Navy until the early 1970s.)
Transfer to Pakistan
In 1963, USS Diablo was loaned to Pakistan on a four-year basis under terms of the Security Assistance Program (SAP) with an option to renew or purchase afterwards. On 1 June 1964, the Pakistani ensign was raised and USS Diablo became PNS Ghazi.
USS Diablo was selected as the freshly-done Fleet Snorkel upgrade would give the Pakistani navy a quality asset, but would not take one of the more valuable GUPPY-upgraded WWII submarines out of American use.
PNS Ghazi arrived at her new homeport of Karachi, Pakistan in September 1964. PNS Ghazi was Pakistan’s first-ever submarine.
(PNS Ghazi arrives at Karachi, Pakistan in September 1964.)
THE 1965 WAR
The 1965 Indo-Pakistani War was the culmination of several border disputes. The war started on 5 August 1965. PNS Ghazi was assigned to patrol south of West Pakistan, and ordered to seek out only “major” Indian warships, understood to be carriers, cruisers, and possibly large destroyers. India tried throughout the war to de-escalate the conflict and limit it as much as possible to a regional ground war. As such, PNS Ghazi‘s prime target; the aircraft carrier INS Vikrant; was not to be found.
(INS Vikrant had been launched as HMS Hercules by Great Britain during WWII but left unfinished when WWII ended. The incomplete carrier was later bought by India and finished to Indian specifications.)
The Indian navy was on the lookout of PNS Ghazi and the submarine had to be wary of detection. On 9 September, the Indian frigate INS Beas made an unsuccessful depth charge attack. Later an Indian Alize ASW plane flew directly over PNS Ghazi while the submarine had the snorkel mast and periscope exposed. It was a miracle that the plane didn’t detect the submarine.
(The cramped control room of PNS Ghazi.)
On 17 September 1965, PNS Ghazi acquired a surface contact which was identified as the frigate INS Brahmaputra, one of the Indian navy’s more modern warships at the time. PNS Ghazi fired three WWII-era Mk14 torpedoes at the contact and increased depth to evade counter-attack. According to the submarine’s logs, three distinct explosions were heard at the time the torpedoes should have impacted, and PNS Ghazi was credited with sinking INS Brahmaputra.
(A photo taken inside PNS Ghazi’s engine room during the 1965 war. The Fleet Snorkel-converted submarines retained their WWII propulsion system, four Fairbanks-Morse diesel engines and two Elliot electric motors.)
In fact, INS Brahmaputra was not sunk, and had not even been hit. The frigate never acquired either a submarine nor incoming torpedoes, and had not dropped any depth charges. No ships were damaged or sunk in the area. It’s unknown to this day what PNS Ghazi‘s target was or what the three explosions were.
The war ended on 23 September 1965 and PNS Ghazi was recalled to Karachi.
Refit in Turkey
The USA placed a weapons embargo on Pakistan in 1965. PNS Ghazi badly needed a refit at that time. To circumvent the embargo, Pakistan negotiated a shipyard deal with Turkey. Turkish shipyards were well familiar with WWII-vintage American submarines as the Turkish navy was operating several. Moreover, in 1953 Gölcük Shipyard in Turkey had been provided the Fleet Snorkel blueprints and had actually done two Fleet Snorkel conversions, on TCG Gür and TCG Inonu (formerly USS Chub and USS Brill during WWII) which had transferred unmodified in 1948. The refit cost $1.5 million ($11.1 million in 2015 dollars) which was a fairly good bargain.
(PNS Ghazi in Karachi harbor in 1970, following the Turkish refit.)
Because the Suez Canal was still closed from the Arab-Israeli Six Day War, PNS Ghazi had to go the long way around South Africa and up through the Atlantic. The refit started in March 1968 and was completed in April 1970. It’s believed that the WWII American mines PNS Ghazi used in 1971 were bought “under the table” from Turkey at this time.
The Daphne class
In 1970 Pakistan purchased three Daphne class submarines from France. This design was much more quiet and modern than the WWII-veteran PNS Ghazi, however the American-built submarine was retained for having exceptionally long patrol range, as the Tench class had originally been designed to fight the Japanese across the wide expanse of the Pacific.
THE 1971 WAR
This war was the final result of the August 1947 partition of British Raj India into the independent nations of largely-Hindu India and largely-Muslim Pakistan. Pakistan was created as a bisected country, with it’s “core” in the west and a distant exclave surrounded by India on three sides, East Pakistan. East Pakistan shared a common religion but little else. Very poor, the area was ethnic Bengali and resented how West Pakistan dominated the country. The Pakistani military was overwhelmingly from West Pakistan.
An insurgency started in East Pakistan after a disputed 1970 election. By the summer of 1971, thousands of ethnic Bengali refugees were pouring across the border into India, straining the country’s economy. At the same time, the Pakistani government stirred up anti-Indian feelings in West Pakistan. By the end of July 1971, it seemed more and more likely that the crisis would end in war.
In August 1971, India transferred the aircraft carrier HMS Vikrant from the western fleet at Bombay to the eastern fleet at Vishakapatnam. This forced Pakistan to adjust it’s submarine planning, as the Daphne class lacked the range to sail all the way around the subcontinent. Despite PNS Ghazi‘s age, the WWII-veteran submarine was selected for the mission.
(PNS Ghazi at sea.)
The aging PNS Ghazi was well-maintained by her crew but by 1971, was experiencing regular equipment failures. Compared to Karachi, the submarine maintenance facilities at Chittagong were poor and there were concerns that even if PNS Ghazi managed to sink INS Vikrant, that the submarine could not receive needed upkeep in East Pakistan and would be marooned pierside there.
The Pakistani mission
As early as 1947, the Pakistani high command realized that East Pakistan was militarily indefensible, and set in on a strategy of “defending the East in the West”, that is to say, to deter an Indian invasion of East Pakistan by launching attacks from West Pakistan against targets in western India, inflicting unacceptable damage there.
As the crisis in East Pakistan deepened in the summer of 1971, the Pakistani government realized that India would eventually be forced to step in. A prime goal for the Pakistani navy was to sink the aircraft carrier INS Vikrant. This would be a colossal blow to the Indian navy outright, and would also lessen the pressure on East Pakistan during any war.
The mission of PNS Ghazi was initially discouraged by the Pakistani admiralty due to the extreme risk of sending a submarine completely around the subcontinent to attack the enemy’s flagship in it’s home waters. None the less, the Pakistani government was adamant. The new Daphne class submarines lacked the range to complete the mission, so it fell to the WWII-veteran PNS Ghazi.
PNS Ghazi was placed under the command of Commander Zafar Muhammed Khan. A British-educated career officer, Cdr. Khan was known for exceptional courage and taking on tasks other officers shunned. PNS Ghazi was his first command, although he had previously been the submarine’s weapons officer during an earlier tour.
PNS Ghazi‘s mission was two-fold. The primary goal was to find and sink INS Vikrant. The secondary objective, to be accomplished with or without the primary, was to mine India’s eastern seaboard.
PNS Ghazi departed port for what would be the final time on 14 November 1971.
(A map of PNS Ghazi’s final voyage.)
The Indian deception
The commander of India’s eastern fleet, Vice Admiral Nilakanta Krishnan, had anticipated that Pakistan might use PNS Ghazi to attack INS Vikrant in any future war; although he predicted the Pakistanis would try it in the Bay Of Bengal, not right off of Vishakapatnam. In either case, his plan for protecting the carrier was centered on a well-planned set of deceptive measures.
On Saturday 13 November, INS Vikrant and her escorts left Vishakapatnam with little notice. The crew was not informed of their destination, which was the Andaman Islands, India’s distant chain of small islands far to the east, near Burma and Thailand. The Pakistanis would probably never think to look for an aircraft carrier in the Andamans and even if they did, there were few Pakistani naval assets that could venture that far.
(A French-made Alize ASW plane takes off from INS Vikrant during the 1971 war.)
Vice Admiral Krishnan called the commander of Madras naval base, on India’s southern coast (opposite the direction the carrier was actually headed) and told him to make fuel ready for the arrival of INS Vikrant. The HQ at Madras was appalled that Krishnan would discuss such things on a civilian telephone line but none the less proceeded as instructed. Obviously, Krishnan was hoping that the telephone line was bugged, or at least that somebody in Madras would slip up and reveal the supply order.
Back in Vishakapatnam Vice Admiral Krishnan placed LOGREQs, orders for large quantities of fresh food, as if INS Vikrant (which had already left) was getting ready to go to sea for an extended cruise. Krishnan knew the food vendors were likely exposed to Pakistani spies, and in this case actually hoped for it.
(The destroyer HMS Rotherham during WWII (top) and as INS Rajput (bottom). During WWII, HMS Rotherham was most famous for accepting the Japanese surrender of Sembawang Naval Base in Singapore in 1945. One of the base’s gates, now torn down, was known as Rotherham Gate. The WWII destroyer transferred to India in July 1949.)
The destroyer INS Rajput was selected to be a “fake Vikrant“. The destroyer began broadcasting a massive load of encrypted radio traffic. Normally only an aircraft carrier operating as a task force flagship would transmit this heavy volume of radio messages. A fake humanitarian message was “accidentally” sent unencrypted to “the Vikrant” (by name) informing a fictitious crewman that his mother was ill. It was thought that this “slip-up” would be more believable than a military-themed message. Once all this was done, INS Rajput resumed using her normal callsigns as if nothing out of the ordinary had happened. Thus, the Pakistanis were led to believe that the ghost carrier group was still in or near Vishakapatnam, which is where PNS Ghazi went to hunt.
The tricks appear to have worked. On 25 November, Indian naval intelligence intercepted a Pakistani navy message from their submarine commodore in Karachi stating that “INTEL INDICATES CARRIER INPORT VISHAKAPATNAM”.
Lead-up to the sinking
Just after PNS Ghazi left port, Indian naval intelligence intercepted a Pakistani navy message from Karachi in West Pakistan to Chittagong in East Pakistan, ordering the procurement of submarine-grade lubricant oil for Chittagong. This was a firm clue that the Pakistanis were going to try to run a submarine mission all the way around the Indian subcontinent.
PNS Ghazi passed the latitude of Bombay (today Mumbai) submerged in the Arabian Sea on 16 November 1971 and rounded Sri Lanka on 19 November 1971. It’s believed that the snorkeling PNS Ghazi was noticed by an Indian fishing trawler that date. Vice Admiral Krishnan had offered training to the Indian merchant marine in identifying signs of a submarine prior to the conflict. On 25 November, PNS Ghazi passed the latitude of Madras, now going northbound searching for the INS Vikrant battle group, which of course was actually hundreds of miles away.
At 16:00 on 1 December, Vice Admiral Krishnan informed the government that he felt certain a Pakistani submarine was operating off India’s east coast, and that he was initiating a search for it.
On 2 December, INS Rajput made an unsuccessful search and returned to Vishakapatnam that day. By this time many Indian sailors already felt war was a matter of when, not if.
At 17:40 on Friday, 3 December 1971, Pakistan launched operation “Chengiz Khan”, a large preemptive airstrike from West Pakistan against targets in northwestern India. The goal was to emulate the success of the Japanese strike against Pearl Harbor during WWII or the Israeli strike against Egypt in 1967. The operation was a failure as the Indian air force was already on a war footing and ready for a surprise attack.
The final hours of PNS Ghazi
Departure of INS Rajput
With the war now formally underway, INS Rajput was ordered to resume searching for the Pakistani submarine. As a security measure INS Rajput sailed with all navigational systems off, instead relying on a harbor pilot (a local expert seaman familiar with the port channel) to leave Vishakapatnam.
If INS Rajput failed to locate an enemy submarine, the destroyer was to head north and rendezvous with the INS Vikrant battle group, now departing the Andamans at full speed. There was no longer any need for tricks, as INS Vikrant‘s planes would soon be bombing East Pakistan anyways.
INS Rajput was not in the greatest of condition, with one engine partially broke-down. The old WWII destroyer had actually been sent to Vishakapatnam just before the crisis started for decommissioning. Both the Fleet Snorkel-upgrade PNS Ghazi and Pakistan’s new Daphne-class were more than a match for the WWII Royal Navy destroyer; additionally the Indian navy (rightfully) feared that Pakistan would lay mines off Vishakapatnam. INS Rajput‘s Captain, LtCdr. Inder Singh, was told that there was a decent chance his ship would not return from it’s mission.
Indian version of events
At 23:40 on 3 December, six hours after the war started, INS Rajput pushed off from the pier at Vishakapatnam, blacked out and under the guidance of a harbor pilot. As INS Rajput was proceeding down the Vishakapatnam harbor channel, it occurred to the captain that an opportune time to attack his ship would be at the dolphin buoy, the final outbound marker where the destroyer would have to momentarily stop to allow the harbor pilot to leave by small boat. He ordered INS Rajput to immediately stop, and sent the harbor pilot off right there in the channel. For the remainder of the outbound leg down the channel, he used his own crew’s navigators, and also gradually increased speed so that by the time INS Rajput reached the dolphin buoy (about 00:00 on 4 December), the destroyer was at combat speed instead of slowing to stop.
In the Indian navy, it was standard practice for less-capable warships to randomly drop occasional depth charges during wartime to discourage any undetected enemy submarine stalking it. INS Rajput began making depth charges ready.
(The Mk.VII depth charge was the Royal Navy’s main depth charge during WWII. It had a 290 lbs warhead and a maximum depth between 300′-500′. It could be rolled off rails or thrown by the Mk.IV DCT, as shown here. INS Rajput’s depth charges in 1971 were these WWII types and most likely leftovers from WWII production.)
At 00:14 on 4 December 1971, INS Rajput‘s sonar room reported what sounded like a submarine changing depth, a ½ mile ahead. Captain Singh ordered a sharp turn and immediately fired two depth charges from the WWII-era Mk.IV DCTs. Less than a minute later, at 00:15, a massive underwater explosion shook the destroyer. The crewmen of INS Rajput were unsure what had happened; some sailors briefly thought their destroyer had been torpedoed due to the force of the explosion. Lookouts on INS Rajput saw what was possibly an oil slick in the area. Singh felt certain he had sunk a Pakistani submarine and relayed this to Vice Admiral Krishnan at Vishakapatnam. Several minutes later, Vice Admiral Krishnan was informed that a beach patrolman in Vishakapatnam had also heard a double explosion at 00:15.
INS Rajput then departed the area and proceed to join up with the INS Vikrant battle group. After sunrise, local fishermen saw an oil slick and some floating debris in the area. Included in the debris was an unused submariner life vest labelled “USS DIABLO”.
Pakistani version of events
The official Pakistani navy account (which slightly changed several times over the years) is that the fleet command in Karachi issued a “weapons live” order on 26 November 1971, the final permission to attack INS Vikrant if found. By this date, the decision to go ahead with operation “Chengiz Khan” a week later had been made, and the military benefit from sinking INS Vikrant would have been so great that it was judged worth possibly sacrificing the air force’s element of surprise.
According to Pakistan, PNS Ghazi commenced laying a small minefield east of the Vishakapatnam harbor mouth on the overnight of 2-3 December 1971. Per orders, the mines were spaced 150 yards apart and set at a depth of about 100′. Pakistani historians feel that most likely, PNS Ghazi had laid part of a minefield that night, then at daybreak on 3 December headed out to deeper water to search for the INS Vikrant battle group. Not finding it, PNS Ghazi returned to the Vishakapatnam harbor mouth area at sunset to resume laying the minefield.
The Pakistani account is adamant that it was not the depth charges of INS Rajput which sank PNS Ghazi. Possibly PNS Ghazi became disoriented as with the war now underway on 3 December, some lights ashore were blacked out; and PNS Ghazi may have misjudged her position and doubled back into her own minefield around midnight; about 10-15 minutes before the INS Rajput depth charging. An alternate possibility is that between 00:09 and 00:14 on 4 December PNS Ghazi saw the blacked-out INS Rajput approaching fast on a collision course, and crash-dived to avoid being rammed. Due to the sea depth being half the length of the submarine, PNS Ghazi may have impacted the seafloor before pulling out of the dive, causing either a battery compartment rupture and hydrogen explosion, or an accidental detonation of a mine in one of the torpedo tubes. The Pakistanis feel that the large explosion caused by INS Rajput‘s depth charges was a laid mine being detonated by the concussion, and that PNS Ghazi had already sunk several minutes before.
Egyptian observer’s account
An Egyptian navy officer happened to be at Vishakapatnam naval base that night. He stated that he recalled hearing two distinct distant explosions, and only then seeing INS Rajput and another ship (which he described as either a minesweeper or salvage ship), depart the base area.
The Egyptian’s timeline runs contrary to all Indian accounts of the incident. Cdr. GC Thadani, stationed at Vishakapatnam, recalls an urgent delivery of damage control equipment to INS Rajput (it had been removed in anticipation of the destroyer decommissioning), watching it leave port, and then still having enough time to return home before he also heard the offshore explosion.
Confirming the kill
Vice Admiral Krishnan was certain that PNS Ghazi had been sunk, but as this would be the first submarine sinking in the Indian navy’s history, he wanted to be absolutely certain. He had already been shown the American-made life vest on 4 December. A smallcraft surveyed the area later that day and reported that what appeared to be a sunken submarine was on the seafloor. Mindful that it may have been a sunken Japanese or Allied submarine from WWII, Krishnan still sought more evidence.
At sunrise on 5 December, the patrol boat INS Akshay arrived with a scuba diver team. There was still an oil slick and a few pieces of debris in the area. A master diver, Lt. Sajjan Kumar, dove down and inspected the wreck. Comparing it to a photo in Jane’s Fighting Ships, he identified it as PNS Ghazi. Kumar reported that the wreck was on the seafloor at 99′ depth, upright with it’s bow pointed towards Vishakapatnam. The senior diver aboard INS Akshay, Lt. Sridhar More, agreed.
(An Indian sketch of PNS Ghazi’s position on the seafloor.)
At 09:14 on 5 December, Vice Admiral Krishnan notified the Indian navy’s GHQ, but not the civilian government, that PNS Ghazi had been sunk.
On 6 December, the Indian navy’s Soviet-built submarine rescue ship INS Nistar arrived with a specialist underwater salvage team. The team reported that the entire forward third, about 100′, of the submarine was destroyed and blown outwards on the starboard side. The hull was as Lt. Kumar had already described, and now settled about 6’6″ into the muddy seafloor. The periscope was raised. The outer hull had damage throughout, but the forward half was almost completely destroyed. Divers were able to access the upper sail hatch, but not any of the hatches leading to the actual inside of PNS Ghazi. Late in the day, finally the aft deck hatch was opened. However the compartment was full of twisted piping and debris and the divers could not proceed in.
On 7 December, at 11:55, the lower conning tower hatch was opened and divers entered the control room of PNS Ghazi. Some of the material taken out was a chart detailing the voyage from Karachi, the captain’s stationary pad, the ship’s log, radio messages, a Pakistani flag, and the characteristic American “flying bridge” curved windshield. These items were presented to Vice Admiral Krishnan that evening. The next morning, they were flown to New Delhi for inspection by government officials. The following day, 9 December, the Indian defense minister formally told the Indian parliament that PNS Ghazi had been sunk.
(The windshield after being raised.)
(A radio message recovered from inside the sunken PNS Ghazi.)
As is the worldwide naval custom, India intended to treat the sunken submarine as a war grave and leave the dead crew interred. Four bodies had to be removed to access the submarine’s interior; they were reburied at sea with military honors.
Clearly, PNS Ghazi was not sunk by the two depth charges alone, as the mangled forward hull was blown outwards, not collapsed inwards.
While it’s certainly possible that PNS Ghazi struck one of her own previously-laid mines, the damage pattern again would indicate that something else had to have happened as well.
Hydrogen explosion: Lead-acid batteries (such as the Sargo type on PNS Ghazi) produce hydrogen gas during their charge / discharge cycles, which is violently flammable. Normally this is dissipated by fans into the submarine’s general ventilation. Worldwide over the years, hydrogen explosions aboard submarines are sadly not uncommon. The log book of PNS Ghazi, which was recovered by India after the sinking, had some entries regarding the battery hydrogen gas levels being periodically high. If the cause of PNS Ghazi‘s sinking was solely a hydrogen explosion, it is possible that aboard PNS Ghazi, an excessive amount of hydrogen had built up and was ignited by a spark either while diving to evade INS Rajput or from shorting wires dislodged by INS Rajput‘s depth charges.
Typically on a submarine which has suffered a hydrogen explosion, the very intense heat ignites anything flammable for the few seconds before the submarine floods out. There was no evidence of metal charring on any debris, moreover items of cloth and paper were recovered unburned by the Indians.
An Indian submarine captain, Cdr. Shafi Sayad, was aboard INS Nistar as a reference specialist and stated that he felt a hydrogen explosion was the most likely cause; either by itself or in combination with the subsequent fire detonating weapons in the torpedo room before the fire had a chance to spread around PNS Ghazi.
Detonation of a mine inside the submarine: This theory has been often cited, usually by sources less familiar with military technology. PNS Ghazi used one of three American WWII submarine-laid mine types.
The Mk10 was either magnetic- or contact-fuzed and had a 420 lbs TNT warhead. The magnetic-fuzed version had several safeties; the primary being an external switch activated by 16′ of sea pressure and the secondary being a rod which rested against the torpedo tube and only extended when the mine exited the tube. Finally, a Type CD-9 timer counted down 170 minutes to allow the submarine to clear the area. The contact-fuzed version was even safer, by default the detonator rod was jammed into the safe position and only extended when the weight of the anchor pulled it out.
The Mk12 was the most common US Navy submarine-laid mine during WWII and was responsible for sinking 27 Japanese ships. It was magnetic-fuzed and 7’9″ long, and weighed 1,445 lbs with a 1,060 lbs TORPEX warhead. It’s safety was a lanyard which attached to the torpedo tube, when laid the lanyard snapped taut as the mine exited the tube, starting the safety countdown clock.
The Mk17 had been designed towards the end of WWII and very few were in use by the time Japan surrendered. It saw some export after WWII. The Mk17 was a magnetic influence mine. It’s safeties were even more robust. A water-soluble plug dissolved after some time in seawater, starting a preset delay between 45 minutes to 100 days. Additionally the M-11 magnetic trigger needed two “looks” on a target before it would detonate the mine.
With any of these mines, it’s nearly impossible to imagine a set of circumstances where one would self-detonate inside the submarine on it’s own. It is, in theory, possible that INS Rajput‘s depth charges damaged a tube with a mine inside it, somehow detonating it. Another factor to consider is that by 1971, the explosives in these WWII mines were a quarter-century old and thus less stable during a fire. Finally when PNS Ghazi‘s log was retrieved, it was read cover to cover by the Indians and there was no indication that PNS Ghazi‘s crew had ever practiced with mines.
Seafloor impact: Vice Admiral Krishnan himself said that he felt this was the most likely cause (many in the Pakistani navy at the time felt the same). In trying to crash dive to avoid a collision with INS Rajput, PNS Ghazi took too steep of an angle and struck the seafloor, somehow causing detonation of a ready mine inside one of the torpedo tubes, which in turn detonated the whole torpedo room.
Remainder of the war
With PNS Ghazi out of the picture, the INS Vikrant battle group had pretty much free reign in the Bay Of Bengal. The entire Pakistani fleet in the east was lost. Pakistani forces in East Pakistan surrendered on 16 December 1971, and the area became the independent nation of Bangladesh. In the west, the Indian army pushed Pakistani troops back across the border and maintained a cease-fire for about a year, when both countries returned to their pre-war borders.
India continued to extract items off the PNS Ghazi wreck for some time. One item was PNS Ghazi‘s control room clock, which was stopped at 00:15, seemingly validating the timeline provided by INS Rajput.
(Some miscellaneous items recovered by India off PNS Ghazi; a bulkhead frame, a hatch with it’s closure spring, and a section of pneumatic tubing.)
Both the USSR and USA offered assistance to India to raise the wreck, which was refused.
PNS Ghazi was the first submarine sunk in combat since the end of WWII. The 1971 encounter with INS Rajput marked the final time a WWII-vintage surface ship and WWII-vintage submarine would battle one another with WWII-era weapons.
Although it ultimately failed, the nearly-3,000 mile voyage of PNS Ghazi was extremely daring and had it succeeded, would have changed the balance of power during the war. The Indian efforts, both the deception and then the actual combat, were likewise decisive. After the sinking of PNS Ghazi, India has never again faced a credible naval threat in the Bay Of Bengal.
To replace PNS Ghazi, in 1975 Pakistan purchased the Portuguese navy’s Daphne class submarine BRP Cachalote, joining the three Daphne class already in Pakistani service. It was renamed as the “new” PNS Ghazi and served until 2006.
(Pakistan’s modern Daphne class submarine PNS Ghazi (S-134), a replacement for the earlier (S-130) submarine lost in 1971.)
The whole crew of PNS Ghazi was proclaimed shaheed, or islamic martyrs, and the Pakistani naval office in Islamabad was renamed after the submarine’s captain, Cdr. Zafar Khan. Cdr. Khan was posthumously awarded the Hilan-i-Ju’rat medal.
Prior to the 1971 war INS Rajput had been slated for immediate decommissioning. After the sinking of PNS Ghazi, the Indian navy decided to defer this despite the old WWII veteran ship’s obsolescence and poor material condition. INS Rajput served another five years after the war and finally decommissioned in 1976. The name lives on aboard the “new” INS Rajput, a Soviet-built guided missile destroyer which commissioned in 1980 and is still in service as of 2015.
(INS Rajput during a friendship visit to Sydney, Australia.)
LtCdr Inder Singh, the captain of INS Rajput during the war, was promoted and decorated with the Vir Chakra medal, and later retired as a commodore.
Vice Admiral Krishnan, the master of the deception, was promoted to Admiral and awarded the Param Vishisht Seva medal. He retired in 1976 and wrote a book called No Way But Surrender, an account of the naval part of the 1971 war. He died in 1982.
(The Beach Road Monument in Vishakapatnam, dedicated to India’s 1971 naval victories including the PNS Ghazi sinking.)
In December 2003, the Indian navy sent a team of ten divers to observe what, if anything, remained of the wreck. The team found the sunken PNS Ghazi completely covered with fishing nets it had entangled over the decades. The outer skin, thin sheet metal dating to WWII, had largely rusted away exposing the frames and external piping outside of the pressure hull. The entire wreck was covered with coral and barnacles, and nothing more than what was already known could be learned.
(Footage of the wreck from an underwater camera in December 2003.)