Notes: In 1963, this WWII-design submarine underwent the USN’s “Fleet Snorkel” update. The “Fleet Snorkel” (FS) program originated when Congress refused to fund any further GUPPY upgrades of WWII-veteran subs. It involved deleting all guns, installing air conditioning, a snorkel, and streamlined sail; but none of the other GUPPY upgrades. As they kept their WWII batteries and hull lines, they were significantly slower underwater than the GUPPYs.
Diablo was loaned to Pakistan under terms of the Security Assistance Program (SAP) in 1964. A major factor in selecting this type was it’s good range, enabling “shuttle” patrols between West and East Pakistan. During a 1968-1969 overhaul in Turkey, Ghazi was equipped to lay mines and also fitted with primitive ELINT and SIGINT gear
Only a year after her arrival, Ghazi set off on her first war patrol, tasked with destroying Indian warships near Bombay. While en route, the Indian frigate INS Beas attacked Ghazi with depth charges unsuccessfully on 9 September. Two days later, an Indian Alize ASW plane made another unsuccessful attack. On 17 September, Ghazi sighted the Indian destroyer INS Brahmaputra and attacked with four torpedoes. Ghazi’s CO logged three explosions and was credited with sinking Brahmaputra, however no area shipping was attacked that day and Brahmaputra returned to port unscathed. It is unknown what the “explosions” were as Brahmaputra never counterdetected Ghazi or dropped depth charges.
1971 War & loss
On 14 November 1971, Ghazi again sailed into combat, with orders to proceed south from Karachi in West Pakistan, go north of the Maldives, south of Sri Lanka, and then turn sharply inland and hug the east Indian coastline all the way up to East Pakistan; mining and attacking Indian warships with the carrier INS Vikrant her prime target. Indian naval intelligence had intercepted a supply request for USN-grade submarine oil from a naval base in East Pakistan, so they were anticipating Ghazi’s patrol plan and probable path. To deceive Pakistani intelligence as to Vikrant’s whereabouts (actually at sea in the Bay of Bengal), the Vishakapatnam naval base continued to order rations as if Vikrant’s crew was in port, and the destroyer INS Rajput (home ported at Vishakapatnam) transmitted a huge volume of HF messages, as if she was the carrier.
The exact circumstances of what happened next are unclear. The official Indian navy account is that Rajput acquired a sonar contact near Vishakapatnam harbour at around 23:59 on 3 December 1971 and commenced a depth charge attack, with an explosion heard and an oil slick observed about twenty minutes later, approximately 00:15 on 4 December 1971.
However an Egyptian submarine officer in Vishakapatnam during the war recalls hearing two distinct explosions and only then seeing Rajput and another ship (either a minesweeper or salvage ship) leave port and sortie towards the area.
Later on 4 December, fisherman found debris (including unused submariner life vests) floating in the area. The Indian salvage ship INS Nestin located the wreck on 5 December. Divers reported that Ghazi’s pressure hull had exploded outwards from the bow, rather than an internal-facing puncture typical of a depth charging. It was suggested that Rajput’s depth charges injected a saltwater leak into the lead-acid batteries, causing a hydrogen gas explosion. However there was little internal charring to support this. It should be noted that although the damage review does not suggest Rajput sunk Ghazi, divers recovered Ghazi’s clock which had stopped at 00:15, supporting the destroyer’s timeline.
It’s most likely that Ghazi accidentally detonated a mine still in the tube, perhaps while trying to hastily unload it to reload the tube with a torpedo. It is also possible that Ghazi struck a mine she had just laid while evading a surface ship (possibly Rajput) causing a larger secondary outward explosion from the torpedo room. A third possibility is that depth charges from Rajput detonated a floating mine; the shock of which caused another mine still aboard Ghazi to detonate.
The Indian navy recovered s significant amount of debris to verify the sub’s identity; including logs and the captain’s personal stationary. Both the USA and USSR offered to raise the hulk but India refused and the wreck has now been swallowed up by the muddy seabed near Vishakapatnam.
(Debris from Ghazi including a hatch, pneumatic tubing, and part of a bulkhead.)
Displacement: 1570t surfaced, 2414t submerged Dimensions: 311’8”x27’4”x15’3” Machinery: Diesel-electric: 4 Fairbanks-Morse diesels, 2 Elliot 2740H electric motors (+2 126-cell batteries), 2 shafts Max speed: 20kts surfaced, 12kts snorkeling, 8.75kts submerged Diving depth: 400’ test, 550’ crush Range: 11,000NM @ 10kts on diesels (75 days max endurance), 97NM @ 2kts submerged on batteries (48hrs max submerged endurance) Complement: 76 (9 officers, 69 enlisted)
x10 (6 fwd, 4 aft) 21” tubes for 24 torpedoes: USN Mk14, 4 ¾ NM max
SS-2 (I) 38NM against large ships, 21NM typical, 7NM against low-flying aircraft (range, bearing)
Type WFA-1 2NM active/passive (range, bearing)
Type NDA fathometer