(DEFENCE SECURITY ASIA) — Retired Vice Admiral Sanjay Mahindru, India’s former Deputy Chief of Naval Staff and first commanding officer of INS Arihant, has warned that Pakistan’s eight Hangor-class submarines will become a “massive headache” for the Indian Navy.

His assessment matters because it identifies an asymmetric undersea threat capable of imposing disproportionate surveillance, escort, and readiness demands upon India’s larger fleet without Pakistan needing to achieve conventional naval superiority across the wider Indian Ocean.

Speaking during a September 2026 defence interview, Mahindru said eight boats could place four or five submarines at sea simultaneously, confronting Indian commanders with multiple concealed threats against warships, harbours, sea lanes, and maritime infrastructure.

“It is never a submarine-to-submarine game,” Mahindru cautioned, arguing that simply acquiring additional Indian submarines cannot substitute for persistent underwater domain awareness, integrated sensor networks, rapid data fusion, and forces capable of prosecuting fleeting acoustic contacts.

His most striking observation, that he would “love to be the submarine commander on the other side,” framed the Hangor threat as an operational opportunity created by concealment, endurance, target density, and India’s geographically dispersed maritime commitments.

The warning does not establish that Pakistan will dominate the Arabian Sea, because India retains substantially greater surface, aviation, surveillance, and nuclear-submarine capacity, but it highlights how modern diesel-electric submarines can complicate operations by exploiting uncertainty rather than numerical parity.

Pakistan ordered eight Hangor-class boats in 2015 under an estimated US$4 billion to US$5 billion programme, with four constructed in China and four scheduled for local construction, creating its largest and most consequential submarine modernisation effort.

Derived from China’s CSOC S26 export design and the Type 039A/B Yuan family, the approximately 2,800-ton Hangor combines diesel-electric propulsion with Stirling-cycle air-independent propulsion, enabling prolonged submerged operations while reducing exposure from frequent battery-recharging snorkel activity.

PNS Hangor was commissioned in China on April 30, 2026, before reaching Karachi in June, while Shushuk, Mangro, and Ghazi entered varying stages of launch or sea trials ahead of their projected induction through 2027–2028.

The four Pakistani-built submarines are progressing more slowly at Karachi Shipyard, meaning the full eight-boat force may not materialise until the late 2020s or early 2030s, leaving delivery schedules, readiness generation, and maintenance capacity as critical uncertainties.

Nevertheless, even partial fleet introduction changes Indian anti-submarine warfare calculations because every additional quiet contact demands localisation, classification, tracking, and potential prosecution across an ocean environment where acoustic conditions, civilian traffic, and operational deception complicate continuous surveillance.

Mahindru linked the vulnerability to India’s “lost decade” in conventional submarine construction, transforming Pakistan’s acquisition from an isolated procurement story into a broader warning about delayed Indian replacement programmes, shrinking force margins, and intensifying Chinese undersea activity.

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Why Eight AIP Submarines Create an Asymmetric Detection Crisis

The Hangor’s decisive operational attribute is not maximum speed or torpedo capacity, but its ability to remain submerged for weeks at economical speed using air-independent propulsion, sharply reducing the detectable snorkelling periods associated with conventional diesel-electric submarine battery recharging.

Stirling-cycle machinery generates electricity by burning stored fuel with liquid oxygen without atmospheric intake, allowing a carefully handled boat to minimise mast exposure, preserve tactical surprise, and wait silently along likely Indian deployment routes or harbour approaches.

Open-source estimates give the class a submerged speed approaching 20 knots, endurance of roughly 65 days under mixed propulsion, six 533-millimetre torpedo tubes, and an approximately 36-person crew, although combat performance and acoustic signatures remain classified.

These specifications do not guarantee survivability, because speed drains energy, machinery produces noise, and effective patrols depend upon crew discipline, oceanography, intelligence, maintenance, and mission planning, yet AIP substantially lengthens the search window confronting Indian forces.

If Pakistan generated four or five operational boats, India could not assume their locations, forcing P-8I maritime patrol aircraft, MH-60R helicopters, surface combatants, sonobuoys, towed arrays, and shore-based sensors to cover numerous possible approach corridors.

This creates a resource-exchange problem in which a concealed submarine consumes far more opposing search effort than its acquisition cost suggests, while false contacts, environmental clutter, and deliberate emissions management can exhaust crews and reduce sensor availability elsewhere.

Indian surface formations approaching Pakistan’s coast would consequently require layered anti-submarine screens, additional airborne coverage, slower route planning, and protected logistics, potentially weakening offensive tempo even when no Hangor achieves a successful torpedo or missile engagement.

Harbour defence becomes equally demanding because Karachi-focused submarines could threaten outbound formations, while Pakistani boats operating farther east could compel India to protect naval bases, commercial shipping, and critical maritime approaches across both peninsular coastlines.

Mahindru’s emphasis on underwater domain awareness therefore addresses the central military mechanism: detection must occur before engagement, and an unlocated AIP submarine retains deterrent value by forcing commanders to plan around a threat that may be absent.

The strategic effect is cumulative rather than decisive, because repeated patrol uncertainty can delay deployments, disperse escorts, elevate insurance and logistics risks, and constrain India’s freedom of manoeuvre without transferring overall command of the Indian Ocean to Pakistan.

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Arabian Sea Sea-Denial Could Complicate Indian Blockade Operations

The northern Arabian Sea offers Pakistan favourable defensive geometry because submarines can operate near supporting bases, intelligence networks, air cover, and maintenance infrastructure while Indian task groups must approach through waters where likely transit routes can be anticipated.

In a crisis, Hangor boats could establish patrol areas around Karachi, Jinnah Naval Base, shipping approaches, or potential Indian blockade lines, forcing New Delhi to dedicate scarce anti-submarine warfare assets before surface forces could operate with acceptable confidence.

This does not make Pakistani coastal waters impenetrable, since India fields P-8I aircraft, MH-60R helicopters, modern surface combatants, and expanding sensor capabilities, but shallow-water acoustics and dense commercial traffic can complicate classification and tracking for every participant.

Pakistan could amplify uncertainty by combining submarines with shore-based CM-302 supersonic anti-ship missiles, maritime aviation, mines, and surface forces, constructing an anti-access and area-denial network that threatens Indian platforms through several distinct detection and engagement pathways.

The resulting battlespace would require India to suppress missile sensors, protect airborne surveillance, clear mines, maintain tanker and ammunition support, and hunt submarines concurrently, increasing logistics footprints and making operational sequencing more vulnerable to disruption or deception.

Hangor’s six torpedo tubes can employ heavyweight torpedoes, anti-ship cruise missiles, and mines, although exact Pakistani weapon configurations remain partly undisclosed, requiring analysts to distinguish demonstrated launch compatibility from assumed operational integration and sustained wartime availability.

Pakistan’s Babur-3 submarine-launched cruise missile, reported with an approximately 450-kilometre range, is frequently associated with the class, but available public evidence has not confirmed full integration, deployment, or routine operational carriage aboard commissioned Hangor submarines.

If nuclear-capable Babur-3 integration occurred, Pakistan could claim a survivable sea-based retaliatory layer, although a diesel-electric attack submarine operating within Indian anti-submarine warfare reach would remain substantially less survivable than a purpose-built ballistic-missile nuclear submarine.

That ambiguity nevertheless affects escalation management because Indian planners must consider conventional and nuclear interpretations of submarine movements, while Pakistan must prevent dual-capable deployments from creating miscalculation, inadvertent escalation, or incentives for pre-emptive tracking during crises.

The credible near-term effect is therefore stronger Pakistani sea denial, not sea control, with Hangor submarines raising the operational price of Indian coastal pressure while remaining dependent upon reliable engines, trained crews, secure communications, weapons stocks, and maintenance cycles.

Bay of Bengal Deployments Could Open a Two-Front Undersea Contest

Pakistani officers have discussed a possible presence beyond the Arabian Sea, including the Bay of Bengal, where even intermittent Hangor patrols could force India to divide anti-submarine warfare attention between western threats and an increasingly contested eastern maritime theatre.

Such deployments would carry symbolic weight because Pakistan has maintained little naval presence there since 1971, but their principal military value would arise from uncertainty imposed upon Indian planners protecting eastern bases, sea lanes, and strategically sensitive patrol areas.

India already monitors Chinese submarines, hydrographic activity, and research vessels across the Bay of Bengal and Andaman Sea, so an additional Pakistani contact could increase P-8I sorties, helicopter detachments, sonobuoy expenditure, and surface escort requirements.

The Andaman and Nicobar Islands anchor India’s surveillance of approaches toward the Malacca Strait, meaning Pakistani operations in adjacent waters could divert assets from monitoring Chinese movements and complicate New Delhi’s broader Indo-Pacific force-posture priorities.

Indian Arihant-class ballistic-missile submarines are widely assessed to use the Bay of Bengal for deterrent patrols, making any foreign submarine presence strategically sensitive even when the intruding platform lacks the sensor performance or endurance required for persistent tracking.

Pakistan would face formidable logistics constraints, however, because sustained eastern deployments require distant maintenance support, replenishment planning, secure communications, oceanographic intelligence, crew endurance, and potentially access arrangements that its present submarine-support architecture may not readily provide.

Transit itself could expose a Hangor to Indian and partner surveillance, while the absence of nearby repair facilities would magnify mechanical risk and reduce patrol availability, limiting the practical frequency of Bay of Bengal operations despite their political signalling value.

China could indirectly influence this equation through technical assistance, intelligence sharing, or port access, but available information does not establish an operational support arrangement, and assuming automatic Chinese participation would overstate evidence while understating escalation risks.

Even rare deployments could still achieve strategic signalling by demonstrating reach, testing Indian detection networks, collecting acoustic intelligence, and compelling New Delhi to plan for two-ocean anti-submarine warfare coverage during periods of heightened Pakistan–India or China–India tension.

The likely consequence is additional friction rather than Pakistani control of eastern waters, yet friction matters because every diverted aircraft, helicopter, escort, and analyst reduces capacity available for other missions across India’s widening Indian Ocean security perimeter.

India’s Delayed Submarine Replacement Magnifies the Hangor Window

Pakistan’s first Hangor entered service eleven years after the 2015 order, while India’s Project 75I programme for six air-independent propulsion submarines remained unsigned by mid-2026, illustrating how acquisition tempo can alter regional risk before fleet totals decisively change.

Project 75I has spent roughly two decades in planning and negotiation, with German Type 214-derived proposals widely discussed, but even a near-term contract would likely place the first completed Indian submarine around 2032–2033 under optimistic industrial and testing assumptions.

Meanwhile, several Sindhughosh-class Kilo and Shishumar-class HDW submarines are approaching retirement, creating a late-2020s readiness window in which hull availability, refit schedules, and crew pipelines may matter more than nominal Indian fleet strength displayed on paper.

India’s six Kalvari-class Scorpène submarines provide modern conventional capability, but they entered service without air-independent propulsion, while plans to integrate an indigenous AIP plug during future refits remain subject to engineering validation, schedule risk, and availability costs.

This mismatch explains Mahindru’s “lost decade” description because submarine construction cannot be accelerated instantly; specialised steel, pressure-hull fabrication, combat-system integration, sea trials, certification, crew training, and dockyard capacity impose long lead times after political approval.

Simply ordering more boats would therefore leave an immediate surveillance deficit, whereas investments in seabed sensors, unmanned underwater vehicles, deployable arrays, maritime patrol aviation, and networked processing could improve detection coverage before new Indian submarines become operational.

India must also protect anti-submarine warfare availability by maintaining P-8I mission systems, stocking sonobuoys and lightweight torpedoes, expanding MH-60R support, and ensuring surface combatants possess reliable towed-array sonars, trained operators, and sufficient operational flying hours.

Force posture becomes central because sensors concentrated near major bases may leave patrol gaps elsewhere, while widely dispersed systems require secure communications, common acoustic libraries, automated correlation, and command arrangements capable of converting detections into timely operational decisions.

Pakistan faces parallel constraints, including Chinese CHD620 diesel-engine reliability after German export restrictions blocked planned MTU engines, local construction delays, infrastructure expansion, crew generation, and the challenge of sustaining high readiness across eleven eventual AIP-equipped submarines.

The undersea balance will consequently depend less upon ceremonial commissioning totals than deployable boats, trained crews, maintenance throughput, weapon readiness, sensor integration, and each navy’s ability to regenerate patrols after failures, losses, or prolonged wartime operations.

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Underwater Domain Awareness Will Decide Whether Hangor Changes the Balance

Mahindru’s proposed remedy places underwater domain awareness above platform-for-platform competition because a submarine that can be continuously detected becomes containable, whereas an unlocated boat can influence fleet behaviour, harbour activity, and political decision-making without firing a weapon.

An effective Indian architecture would combine P-8I radar and acoustic searches, MH-60R dipping sonar, shipborne hull and towed arrays, fixed seabed sensors, unmanned systems, satellite cueing, electronic intelligence, and continuously fused command-level maritime operating pictures.

Hardware alone is insufficient because acoustic classification depends upon environmental databases, operator proficiency, contact history, adversary signature libraries, and algorithms capable of distinguishing submarines from merchant traffic, fishing vessels, biological noise, and changing seabed conditions.

Persistent surveillance also requires a substantial logistics enterprise encompassing sonobuoy inventories, aviation fuel, spare engines, depot maintenance, data links, secure processing centres, and forward operating locations, making anti-submarine warfare an endurance contest across the entire support system.

Pakistan’s effectiveness will similarly depend upon whether Hangor crews can exploit acoustic conditions, coordinate safely with friendly forces, receive useful intelligence without revealing positions, maintain weapons proficiency, and sustain patrol cycles despite engine, battery, or dockyard constraints.

The export design’s actual quieting, sonar sensitivity, combat-system maturity, and reliability have not been independently verified, so claims describing Hangor as either revolutionary or easily detectable exceed the publicly available evidence and deserve equal analytical scepticism.

India’s numerical and technological advantages remain substantial, but those advantages must be present at the correct location and time, because distant assets, grounded aircraft, unavailable helicopters, or unprocessed sensor data cannot neutralise an immediate submarine contact.

Conversely, Pakistan cannot convert eight ordered hulls automatically into four or five persistent wartime patrols, since refits, training, transit, defects, weapon loading, and crew fatigue could reduce operational availability below the optimistic rate invoked by Mahindru.

The programme nevertheless delivers strategic signalling by demonstrating deeper China–Pakistan defence-industrial integration, expanding Karachi’s sea-denial options, and obliging India to allocate resources against a threat that intersects with Chinese submarine activity across the wider Indo-Pacific.

Ultimately, the Hangor class changes the battlespace by multiplying uncertainty rather than overturning naval hierarchy, turning detection, logistics, readiness, and data fusion into decisive measures of power while exposing the cost of India’s delayed conventional submarine recapitalisation.