The Present and Future Threats to Pakistan’s Submarine Fleet

By 2028, the Pakistan Navy (PN) plans to operate three upgraded Khalid-class (Agosta 90B) and eight new Hangor-class (likely S26) air-independent propulsion (AIP) submarines. It is not only modernizing its fleet, but expanding its costlier AIP element by a factor of nearly 4X. The result will be a large sub-surface fleet capable of anti-ship warfare (AShW), anti-submarine warfare (ASW), and long-range land-attack missions.

In terms of sub-surface warfare, the PN’s forthcoming fleet will be a credible force. First, the submarines themselves will be equipped with contemporary subsystems and capabilities. The upgraded Agosta 90B, for example, will leverage soft-kill torpedo countermeasures, a new combat management system (CMS), an electronic support measures (ESM) suite with electronic intelligence (ELINT) capabilities, early warning capabilities through a radar warning receiver (RWR), and other features. Overall, these systems are about as advanced as Pakistan can acquire in the market. Second, the PN will benefit a quantitative element that was never available to it up to this point. Third, the PN is building a support element that will allow it to extract maximum utility from its submarines, such as its very-low-frequency (VLF) communications facility, which will allow it to communicate with its submerged submarines.

The PN’s submarines will not only be the bulk of its offensive capability – i.e., through the ability to launch land-attack cruise missiles (LACM), such as the Babur 3 – but its defensive element as well. Undoubtedly, the PN’s hope is to both deny India the ability to exert itself in Pakistan’s exclusive economic zone (EEZ), as well as undertake long-range strikes well away from Indian territory through stand-off range weapons (SOW). However, India is both aware of the PN’s goals, and, in turn, the Indian Navy (IN) is building perhaps one of the most extensive ASW capabilities in Asia, if not the world, to deter and erode Pakistan’s ‘Silent Service.’ The IN started this process through the induction of P-8A Poseidon long-range maritime patrol aircraft (LRMPA), but it is now adding newer P-8I Neptune variants as well as a large number of corvettes and, with time, a larger conventional submarine fleet to carry its own deterrence and offensive element.

Anti-Submarine Warfare is Not a Trivial Effort

Before delving into India’s ASW efforts, it is important to study the reality of ASW. Simply put, ASW is not an “easy” effort. In the Falklands War, for example, the Argentinean Navy showed that “a poorly manned, poorly maintained diesel submarine can have a tremendous effect on operations for a fleet commander.”[1] In other words, the presence of a submarine in a littoral environment is enough of a threat to force a large and adept navy to pause its campaign, e.g., imposing a maritime exclusion zone (MEZ). The reason for this is that a naval force commander will not put their assets at risk against, basically, an unknown variable.[2]

The Nature of Sound Propagation at Sea

Granted, the Falklands War occurred in a different time, and since then, one would think that technology and concepts would have caught up. However, the reality of how the sea works still poses an obstacle.

The primary means of detecting an object underwater is through sonar, typically using active pulses that would bounce off an object and return an echo, or passively listening for others’ active pulses and echoes. In ‘deep water’ environments, such as the Pacific Ocean, sound could propagate fairly easily because those areas were generally ‘quiet’ – i.e., did not involve much ship traffic or offshore activity – and fairly barren in terms of obstacles that could interfere with acoustic travel.[3]

Likewise, these operational environments were out in the open seas. Each side’s navy could flexibly deploy their respective LRMPAs, frigates or destroyers, and other assets to survey and monitor these areas.

Thus, in America and Russia’s Cold War-era maneuvers, it was easier to decipher the movement, position and state of an enemy submarine (especially a nuclear submarine, which also generated its own acoustic noise if its reactor is actively running). Unfortunately, this is not the case in shallow water environments, especially in littoral areas near coasts, active sea lanes, and other ‘noisy’ areas.

The Practical Realities of Shallow and Deep-Water Environments

In contrast, littoral water environments are “noisier” than deep-sea theaters. This difference is a result of the fact that littoral environments see much more use in terms of ship traffic for trade, offshore oil rigs, and a plethora of other factors. Thus, it is more difficult to isolate the noise of a single submarine. Second, because the ocean floor is closer to the surface of the sea, acoustic vibrations do not have enough room to travel. There is a higher chance of hitting obstacles, thus weakening acoustic signals.[4]

One solution to this is to use aircraft and other assets (e.g., thermal imaging), but that requires flexibility in terms of use. In other words, a military is unlikely to deploy LRMPAs or ships to a contested environment that could include enemy surface ships and/or fighter aircraft. However, these systems may help if one is trying to snuff out an intruding submarine in one’s own territory, a concern to both countries. But airborne surveillance and surface based ASW coverage will not guarantee exposing a submarine; rather, they might make it more difficult for the enemy submarine to flexibly operate and execute its mission.

The Reality of the Arabian Sea

Based on the National Geophysical Data Center – NOAA’s data of seafloor depth (available through Google Earth), one can see that the depth of the ‘North Arabian Sea’ (a termed the PN coined to highlight its main areas of operation) is approximately 17,750 feet or less (in contrast, significant swaths of the Pacific Ocean measure at 17,750 feet or deeper. However, the deeper parts of the North Arabian Sea are ‘busy’ in terms of active sea lanes for trade. Thus, combined with the higher seafloor and activity, this area should mask an AIP-equipped Khalid-class or Hangor-class submarine fairly well.

In terms of the Hangor-class specifically, one of the concerns Quwa had raised earlier was that if it deploys a Stirling AIP, it might not be able to fully leverage the AIP’s advantages to the warm water environment of the Arabian Sea. Basically, Stirling AIPs involve moving parts, which will result in vibrations that could travel faster in warm water compared to cold water. However, the inherent realities of the Arabian Sea – i.e., its shallower depths and sea activity – may render this concern moot. Moreover, the coastal areas are likely to mask the Hangor’s acoustic profile, even near India, which could incentivize the PN to undertake offensive attacks against India’s coastal assets (and vice-versa for India against Pakistan).

Currently, India’s ASW investments are likely aimed at eroding this incentive and, at the minimum, push the land attack range of Pakistan’s submarines to a more manageable level. However, even with a massive cadre of ASW assets, unless India imposes sea and air control in Pakistan’s exclusive economic zone (EEZ), it is unlikely to establish an MEZ (basically, a step towards blockading Pakistan). So long as the PN operates a sizable submarine fleet through its Khalid-class and Hangor-class, and the Pakistan Air Force (PAF) is still an active force, the risk to IN assets will be too high. India’s ASW focus is, arguably, defensive in focus.

India’s ASW Investments

If anything, if sub-surface threats are a real problem for India, then logically, they should also be a concern for Pakistan as well. In other words, both navies would need to contend with intruding submarines; thus, the question is, how are these two opting to invest in ASW? Between the IN and PN, the IN is investing at a comprehensive scale, and with a greater diversity of ASW-capable assets.

Anti-Submarine Warfare Shallow Water Crafts (ASWSWC)

India’s Garden Reach Shipbuilders & Engineers (GRSE) and Cochin Shipyard Limited (CSL) both secured the IN’s bid to supply 16 ASWSWCs. GRSE and CSL will each build eight ASWSWCs, and of different designs to the other shipyard. GRSE’s ASWSWC will have a length of 77 m and displacement of 750 tons, and CSL will supply a 74 m ship, but will also have a displacement of 750 tons. Both ASWSWC designs will use waterjets powered by diesel-based systems, offering a top speed of 25 knots, and range of 1,800 nm at 14 knots.[5]

In terms of combat systems, the ASWSWCs’ main complement comprises of two torpedo tubes (likely the standard triple configuration) for lightweight torpedoes as well as an ASW rocket launcher, a cannon, and mine-laying rails.[6] These ships lack anti-ship warfare (AShW) and anti-air warfare (AAW) capabilities, but their sole function is to operate in India’s shallow waters to search and attack intruding enemy submarines in Indian waters. In other words, there are no surface or airborne threats for these ASWSWCs.

The single mission role enables India to control the cost of the ASWSWC, thus enabling it to acquire a large number of these ships. For example, contract with GRSE for eight ASWSWC was priced at $877.94 million US, i.e., $109.74 million US per ship.[7] The cost is still relatively high, but the main driver of it likely stems from the use of waterjets and the complete ASW suite. The waterjets should minimize the hull’s vibration, thus providing it with a minimal acoustic signature (even at higher speeds). In other words, the ASWSWC is better positioned to quietly track a submarine compared to standard propellers.

In any case, with 16 ASWSWCs the IN will maintain a dense surface coverage along its littoral waters. One can expect that in conflict with Pakistan, the IN will deploy most – if not all 16 – of these ships to its west coast so as to limit the operating space available for intruding Pakistani submarines.

Kamorta-Class Anti-Submarine Warfare Corvette

In February 2020, the IN took delivery of its forth Kamorta-class (Project 28) ASW corvette. The Kamorta-class has a length of 109.2 m and total displacement of 3,150 tons. While its main focus is ASW, this ship is a multi-mission platform equipped with AShW and AAW.

The Project 28 and ASWSWC together constitute 20 dedicated ASW surface platforms. However, this does not include the IN’s ASW-capable destroyers and frigates. These will likely be in place to guard the IN’s aircraft carrier(s) in forward deployment more so than guard the coastline. In fact, the benefit of dedicated assets such as the ASWSWC is that the IN does not need to pull frontline assets for ASW. As a result, both its offensive force (e.g., carriers) and defensive element leverage ASW, thus adding to the difficulty for PN submarines to engage the IN in either open waters or closer towards the coast.

Lockheed Martin/Sikorsky MH-60 Seahawk

In February 2020, the Indian government approved the purchase of 24 Lockheed Martin/Sikorsky MH-60 Romeo multi-mission naval helicopters. One of the key features of the MH-60 is Raytheon’s AN/AQS-22 Advanced Airborne Low-Frequency (ALFS) dipping sonar. Raytheon reportedly claimed that the AN/AQS-22 offers four times as much area coverage as competing dipping sonars, and provides active and passive modes for tracking and classifying submarines.[8] Most of these MH-60s will operate from the IN’s frigates, destroyers and large corvette units, but a number of these will likely be available from the shore as well.

Boeing P-8I Neptune

The IN was recapitalizing its LRMPA fleet through the 2010s, with its first tranche nearing completion via 12 aircraft (ordered in 2009 and 2016). In June 2019, India’s Ministry of Defence approved the purchase of another 10 P-8Is.[9] In terms of ASW, the IN’s Neptunes leverage CAE’s AN/ASQ-508A magnetic anomaly detection (MAD) systems, which is mounted to the P-8I’s tail. The main purpose of MAD is surveying areas with the aim of identifying the location of submarines by detecting magnetic variations or shifts. The P-8I can be armed with depth charges, mines, and lightweight ASW torpedoes.

Quantity and Quality

Like its surface-based ASW element, the IN is working towards both a quantitatively large and, without a doubt, qualitatively best-of-class airborne ASW force. It may be difficult to operate the MH-60 and/or P-8I in contested areas, but as with the ASWSWC, the IN will work to saturate the seas near India with both pervasive and extensive ASW coverage. Granted, the IN cannot guarantee finding and stopping a Pakistani submarine, but with these assets at its disposal, it is among a handful of navies that can at least claim to have as standard-leading a surface and airborne ASW element available.

Practically, the availability of a combined 50+ ASW-capable assets allows the IN to develop its situational awareness across multiple modes (i.e., sonar, magnetic, thermal etc) and platforms. In terms of the latter, each asset will leverage data links to share information and, in turn, allow engagement units to coordinate responses. Its engagement assets are diverse, they comprise of high-altitude aircraft (the P-8I), helicopters (MH-60 and potentially others), corvettes, and submarines.

The result of these investments will make a sub-surface intrusion a higher risk proposition for the PN. In one sense, it might not be as much of an issue, at least if the main mission of its submarines is to contest or deny the IN access and control of Pakistan’s sea lanes and coastal areas. However, it could also minimize the offensive threat of the PN’s sub-surface assets, rendering them more of a defensive tool. Granted, if Pakistan continues to develop longer-ranged cruise missiles, it could still present an offensive threat.

In this scenario, the IN would have to worry about Pakistani submarines attacking in-shore Indian targets, but from distant locations. In this case, the IN would have to deploy its long-range ASW assets (e.g., P-8I, corvettes, frigates, destroyers, submarines, etc) closer to the ‘North Arabian Sea.’ However, this will mean entering contested zones, which would raise the risk of ship and/or aircraft losses for both the IN and PN.

With the IN’s ASW investments in mind, it will be worth observing how the PN opts to develop its ASW. If the PN’s sub-surface can intrude towards India, the reverse is also true, but for India’s submarines vis-a-viz Pakistan’s coastal areas. The challenge for the PN is that the bulk of its core ASW assets – e.g., the P-3C Orion LRMPA and Sea King ASW helicopters – are aging. Moreover, the PN does not yet have as large a surface based, dedicated ASW roadmap as India. In fact, its new ASW assets will come as part of multi-mission Type 054A/P and Jinnah-class (MILGEM) frigates, not dedicated systems.

The PN is aiming to acquire a next-generation LRMPA, and an industry source did tell Quwa that the PN is looking for new multi-mission naval helicopters comparable to the MH-60. However, the PN did not set a dedicated ASW (akin to the IN ASWSWC) asset as a requirement, but it might, except differently.

Like the IN, the PN is network enabling its assets so that they can share information and coordinate. And the PN is cognizant of the need of new-generation airborne ASW capabilities, but at sea-level, it may build its coastal anti-access and area-denial (A2/AD) force through submarines (instead of corvettes). The key to achieving this would be its tentative miniature submarine program.

If this program evolves into a true shallow-water attack submarine (i.e., with the ability to deploy both light and heavyweight torpedoes), it could emerge as the PN’s answer to the problem the IN’s ASWSWC is solving. The main difference, however, would be the PN doubling down on the mask its coastal regions provide to submarines and, in turn, leveraging stealth/low detectability underwater to discourage the IN from intruding with its own submarines. But the network-enabled sharing and coordination will still apply.

[1] Lt. Commander Jason C. Pittman. “Zone Defense – Anti-Submarine Warfare Strategy in the Age of Littoral Warfare.” U.S. Army Command and General Staff College. Fort Leavenworth. 12 December 2008. Page 14.

[2] Ibid. Page 14.

[3] Ibid. Page 17-18.

[4] Ibid. Page 19.

[5] “Details of GRSE’s small anti-submarine corvette emerge.” Shephard Media. 13 November 2018. URL: https://www.shephardmedia.com/news/naval-warfare/details-grses-small-anti-submarine-corvette-emerge/ (

[6] Ibid.

[7] Anuradha Himatsingka. “GRSE signs contract for 8 anti-submarine warfare shallow water crafts for Indian Navy.” The Economic Times. 29 April 2019. URL: https://economictimes.indiatimes.com/news/defence/grse-signs-contract-for-8-anti-submarine-warfare-shallow-water-crafts-for-indian-navy/articleshow/69099130.cms

[8] “Fly and Listen: The AN/AQS-22 ALFS Sonar System.” Defense Industry Daily. 02 September 2019. URL: https://www.defenseindustrydaily.com/154m-for-3-aqs-22-alfs-sonars-et-al-03643/

[9] Rahul Bedi. “Indian MoD approves procurement of 10 more P-8I aircraft for Indian Navy.” Jane’s Defence Weekly. 24 June 2019. URL: https://www.janes.com/article/89461/indian-mod-approves-procurement-of-10-more-p-8i-aircraft-for-indian-navy