Undersea Rivalry: Pakistan’s New Submarines and India’s Maritime Challenge
Pakistan is rapidly modernising its submarine fleet with Chinese-origin AIP submarines, creating a new challenge for the Indian Navy in the Arabian Sea. India, however, retains overwhelming advantages in overall naval capability—and is moving to address its conventional submarine shortfall through Project 75(I) and a broader push towards indigenous naval power.
The Indian Ocean is witnessing a quiet but significant transformation beneath the surface.
Pakistan is in the process of replacing its ageing conventional submarine fleet with eight Chinese-origin Hangor-class AIP submarines, while India is moving towards a roughly US$9 billion programme for six advanced conventional submarines under Project 75(I). The developments are being closely watched because submarines are fundamentally different from most other naval platforms: they can remain concealed for extended periods, threaten high-value surface assets and impose uncertainty on an adversary’s freedom of manoeuvre.
For India, therefore, Pakistan’s submarine modernisation is a legitimate strategic concern.
But it needs to be assessed in proportion.
Pakistan is improving one particular element of its naval capability—underwater sea denial. India continues to possess a much larger and more diversified maritime force, including two aircraft carriers, around 13 destroyers, approximately 20 frigates, extensive maritime aviation and three operational nuclear-powered ballistic-missile submarines. The two countries are consequently not engaged in a contest between equivalent naval forces.
The more relevant question is whether Pakistan’s new submarines could exploit a temporary weakness in India’s conventional submarine fleet and complicate Indian naval operations in the Arabian Sea.
The answer is yes.
That is precisely why India’s submarine programme matters.
The 1971 Warning
India’s experience in the 1971 war remains an important reminder of the potency of submarine warfare.
On 9 December 1971, Pakistan’s PNS Hangor sank the Indian frigate INS Khukri, the first warship lost to a submarine since the Second World War. The episode demonstrated that even a relatively small submarine force could impose a disproportionate cost on a surface fleet.
But the broader naval story of 1971 was very different.
Pakistan’s PNS Ghazi was destroyed off Visakhapatnam in early December by INS Rajput. India then demonstrated what broader maritime superiority could achieve. Operations Trident and Python struck Karachi, sinking or crippling Pakistani vessels including PNS Khaibar and PNS Muhafiz, while damaging port infrastructure and fuel stocks.
The naval campaign contributed to isolating Pakistan’s forces and demonstrated the strategic value of maritime dominance. By 16 December, approximately 93,000 Pakistani troops had surrendered, leading to the creation of Bangladesh.
The lesson is not that submarines are decisive by themselves. It is that submarines become strategically powerful when integrated into a wider maritime system of surveillance, surface warfare, aviation, logistics and control of the sea.
That distinction remains relevant today.
Pakistan’s Underwater Modernisation
Pakistan’s conventional submarine force has historically been modest. Before the Hangor programme, it consisted of two ageing Agosta-70 submarines and three Agosta-90B boats equipped with French MESMA AIP systems, subsequently upgraded with Turkish assistance.
The eight-boat Hangor programme represents a substantial improvement.
Ordered from China in 2015, the submarines are based on the Chinese Type 039A/Yuan family or its S26 export variant. The first boat, PNS Hangor, was commissioned in China in April 2026 and arrived in Karachi in June.
Its significance lies primarily in endurance and stealth. Stirling AIP technology allows the submarine to remain submerged for multi-week periods without the need to surface frequently for atmospheric air. Modern sensors and weapons systems further improve its effectiveness in surveillance and sea-denial missions, with potential compatibility with Babur-3 cruise missiles adding another dimension.
Four submarines are being constructed in China, with the remaining three of the Chinese-built batch expected by mid-2027. Four more are being constructed at Karachi Shipyard under technology transfer, although these locally built boats could face delays into the late 2020s or early 2030s.
This programme will give Pakistan a significantly more capable conventional submarine force than it has possessed in the past.
India should take that seriously.
However, the numbers need to be viewed realistically. Pakistan is not suddenly acquiring an undersea fleet capable of matching the Indian Navy across the Indian Ocean. Its strategic objective is much narrower: to make the Arabian Sea more dangerous for an adversary and impose costs on Indian naval operations through concealed, relatively inexpensive platforms.
That is classic sea-denial strategy.
India’s Conventional Submarine Gap
India’s challenge is that its conventional submarine fleet is ageing even as its wider navy expands rapidly.
India currently operates roughly 16–19 submarines, including six modern Kalvari-class Scorpène submarines. The remainder of the conventional fleet comprises older German-origin Shishumar-class Type 209 and Russian-origin Kilo-class Sindhughosh boats, many of which have crossed or are approaching 25 years of service.
The problem is therefore not simply the number of submarines on paper. Operational availability becomes increasingly important as platforms age and require longer refits and maintenance.
This creates a vulnerability that deserves attention.
A navy can compensate for some deficiencies in surface warfare through additional ships, aircraft and missiles. Submarine warfare is less forgiving. A modern AIP submarine operating quietly in a contested sea can impose a disproportionate level of uncertainty on surface forces, particularly high-value assets such as aircraft carriers.
Pakistan’s Hangor programme therefore arrives at an uncomfortable moment for India.
The first Hangor-class boats are entering service now, whereas India’s next generation of AIP conventional submarines will not arrive until the early 2030s.
That creates a temporary window in which Pakistan’s conventional undersea capability will improve while India’s older submarines continue to age.
Project 75(I): The Long-Delayed Answer
India’s answer is Project 75(I), under which six advanced AIP-powered conventional submarines are to be built in India with German technology transfer.
The proposed submarines are based on a customised and enlarged version of the German Type 214 design and will use hydrogen-fuel-cell AIP technology, providing substantially longer submerged endurance—roughly twice that of conventional diesel-electric submarines.
The programme is valued at approximately US$9 billion. Construction is planned primarily at Mazagaon Dock Shipbuilders Limited (MDL), Mumbai, with substantial technology transfer from ThyssenKrupp Marine Systems (TKMS). Indigenous content is expected to rise towards 60% in the later boats, and there is an option for three additional submarines.
The programme’s importance therefore goes beyond the six vessels.
India needs not merely to purchase submarines but to develop the industrial capability to design, build, maintain and eventually improve them domestically. The technology-transfer element is particularly important in that context.
Yet there is no escaping the programme’s history of delay.
As of 18–19 August 2026, the contract has not been signed. Commercial negotiations are understood to be largely complete, while the remaining issues involve final technology-transfer review and approval by the Cabinet Committee on Security (CCS).
Reports from mid-August indicate that the proposal is nearing this crucial stage. An India Today analysis published on 18 August reported that India and Germany are expected to sign the approximately US$9 billion agreement in the coming weeks, subject to the remaining approvals.
Even after signing, however, the first submarine is expected only around 2032–33, approximately seven years after contract signature, followed by one boat a year.
This timing matters.
Pakistan’s Hangor-class submarines will therefore be operating in the Arabian Sea several years before India’s Project 75(I) boats begin arriving.
But the Naval Balance Is Much Larger Than Submarines
This is where the India-Pakistan comparison needs perspective.
Indian Navy vs Pakistani Navy Comparison:
India operates two aircraft carriers—INS Vikrant and INS Vikramaditya. It has approximately 13 destroyers, including the four-ship Visakhapatnam-class Project 15B, and around 20 frigates, with the newer Project 17A Nilgiri-class ships progressively entering service.
India also possesses a substantial maritime aviation capability, including P-8I long-range maritime patrol aircraft, alongside a much larger logistics and support infrastructure.
Pakistan has no aircraft carrier and operates a considerably smaller surface fleet. Its modern core includes four Chinese Type 054A/P Tughril-class frigates, four Zulfiquar-class F-22P frigates and one older Oliver Hazard Perry-class ship. Two Babur-class corvettes are active, with two more under construction for delivery during 2026–27.
Pakistan is also developing additional offshore patrol vessels and smaller craft, while indigenous Jinnah-class frigates remain at the planning stage.
This difference is fundamental.
Pakistan is building a compact navy designed principally to deny an adversary freedom of action in its immediate maritime environment.
India is building a navy designed for blue-water operations and multi-theatre reach.
Its advantages extend across tonnage, aviation, surface combatants, logistics, nuclear deterrence and industrial capacity.
Pakistan’s growing use of anti-ship missiles and unmanned systems is an attempt to strengthen its asymmetric options. That is strategically sensible from Pakistan’s perspective, particularly because it cannot economically replicate India’s overall fleet structure.
But asymmetric capability should not be confused with overall naval parity.
The Nuclear Dimension
The most significant difference lies beneath even the conventional submarine contest.
India now has three operational Arihant-class SSBNs, including INS Aridhaman, commissioned in 2026, with a fourth expected around 2027. These submarines provide India with a sea-based nuclear deterrent.
Pakistan has no equivalent nuclear-powered ballistic-missile submarine capability.
This distinction matters because conventional AIP submarines and nuclear-powered ballistic-missile submarines serve fundamentally different strategic purposes.
The Hangor-class can strengthen Pakistan’s conventional sea-denial posture. It cannot replicate India’s strategic nuclear-submarine capability.
Consequently, Pakistan’s naval modernisation should be seen as a sharpening of its conventional maritime challenge, particularly in the Arabian Sea—not as a transformation of the broader strategic balance.
The Real Concern for India
The real concern is therefore narrower, but also more immediate.
Pakistan’s new AIP submarines will make the Arabian Sea a more difficult operating environment for the Indian Navy during the period before India’s next-generation conventional submarines arrive.
This could complicate the deployment of Indian surface combatants and carrier groups and require greater investment in anti-submarine warfare, maritime surveillance and undersea intelligence.
For India, this is particularly relevant because the Arabian Sea is not simply a military theatre. It carries vital commercial shipping and energy flows and connects India to the wider Middle East and beyond.
A hostile submarine operating covertly in these waters does not have to sink a carrier to have strategic value. The mere possibility of its presence can force a navy to devote additional aircraft, ships, sensors and time to finding and tracking it.
That is the logic of sea denial.
India therefore needs to close the conventional submarine gap—not because Pakistan is becoming India’s naval equal, but because a capable adversary can exploit even a limited gap in one critical domain.
Beyond Pakistan: The Larger Indian Ocean Equation
There is also a broader strategic reason for India to accelerate its undersea capabilities.
Pakistan’s naval modernisation is closely linked to its defence relationship with China. The Hangor programme is therefore not simply a bilateral India-Pakistan procurement story.
The Indian Ocean is becoming increasingly important in the wider strategic competition involving China, India and other regional powers.
India consequently needs a submarine fleet designed not only to address Pakistan but to support its wider maritime strategy.
That requires numbers, endurance, sensors, weapons, maintenance infrastructure and trained crews. It also requires a domestic industrial ecosystem capable of sustaining the fleet over decades.
This is why Project 75(I) should be judged not merely by whether the first submarine enters service in 2032 or 2033.
Its greater value will lie in what India learns to build thereafter.
From Imported Platforms to Indian Capability
India’s naval modernisation is increasingly moving away from the old model of simply buying finished platforms from abroad.
Project 75(I), with its substantial technology-transfer component and rising indigenous-content target, fits into a larger effort to build domestic capability in naval design and construction.
The strategic objective should be clear: foreign technology must become a bridge to Indian capability, not a permanent substitute for it.
If India can successfully absorb advanced submarine technology, build successive boats domestically and develop the supporting ecosystem of propulsion, sensors, electronics, weapons and maintenance, the long-term advantage could be considerably greater than the six submarines themselves.
India’s emerging naval-industrial base is therefore as important as the individual ships and submarines being commissioned.
A Temporary Gap, Not a Strategic Reversal
Pakistan’s Hangor-class submarines are a genuine addition to its military capability and should not be dismissed.
They will improve Pakistan’s ability to conduct sustained submerged operations and strengthen its sea-denial posture in the Arabian Sea. The timing is also significant because these submarines will become operational before India’s Project 75(I) fleet.
For a period, therefore, Pakistan will possess an improving conventional undersea capability while India’s older boats continue to age.
That is a real Indian security concern.
But it is also important not to lose sight of the larger balance.
India has two aircraft carriers against none for Pakistan; approximately 13 destroyers against none; around 20 frigates against a much smaller Pakistani surface fleet; substantially greater maritime aviation and logistics; and, critically, an operational nuclear-powered submarine force.
India also possesses the economic and industrial base required to sustain a much larger navy.
The immediate challenge is to ensure that the conventional submarine gap does not become the weak link in that otherwise formidable maritime structure.
The longer-term challenge is larger still: to create an Indian undersea force that is sufficiently numerous, technologically advanced and domestically supported to deal simultaneously with the Pakistan challenge and the wider strategic competition unfolding across the Indian Ocean.
Pakistan is strengthening its ability to deny the sea.
India’s objective must remain the ability to control and secure it.
That distinction explains both why Pakistan’s submarine modernisation deserves India’s attention—and why it should not be mistaken for a fundamental change in the maritime balance.
The Indian Navy’s challenge is not to match Pakistan boat for boat.
It is to ensure that no adversary can exploit a temporary capability gap to constrain India’s freedom of action in the waters that are vital to its security, trade and energy interests.
For a country whose economic and strategic future is increasingly tied to the Indian Ocean, that is not an option.
It is a necessity.
