Run Silent, Run Deep

Pakistan’s Hangor-class submarines expose not just a shifting naval balance in the Indian Ocean, but also the cost of India’s chronic delays in defence procurement.

The balance of power in the Indian Ocean is increasingly being shaped by vessels that are designed never to be seen. Pakistan’s induction of the Hangor-class submarine represents a calculated shift in Islamabad’s maritime strategy, backed by China, and poses uncomfortable questions about India’s own submarine modernisation.

The Pakistan Navy has made little secret of its ambitions. Having commissioned the first Hangor-class submarine in April 2026 and received the third China-built boat, it has signalled its intention to maintain a sustained naval presence not only in the Arabian Sea but also in the Bay of Bengal. Such deployments would extend Pakistan's operational reach far beyond its traditional theatre and add another layer of complexity to India's maritime security calculations.

The Chinese Connection

The Hangor class is an export variant of China’s Type 039A/039B Yuan-class diesel-electric attack submarine, already in operational service with the People's Liberation Army Navy. The programme illustrates the depth of strategic cooperation between Beijing and Islamabad. Under an estimated USD 5 billion agreement, Pakistan is acquiring eight submarines, with four being built in China and the remaining four assembled at Karachi Shipyard and Engineering Works under a technology-transfer arrangement. It is one of the largest defence-industrial collaborations between the two countries and further cements China’s role as Pakistan's principal military supplier.

The significance of the Hangor class lies less in its numbers than in its technology. Unlike conventional diesel-electric submarines that must periodically surface or snorkel to recharge batteries, thereby exposing themselves to detection, the Hangor is equipped with Air-Independent Propulsion (AIP). Using a Stirling-cycle propulsion system derived from Chinese designs, it can remain submerged for as long as three weeks while operating silently at patrol speeds. For a submarine, invisibility is survival. AIP substantially enhances stealth and complicates the task of anti-submarine forces seeking to locate and track it.

Special Features

The submarines incorporate additional measures to reduce their acoustic signature. Their outer hulls are coated with sound-absorbing rubber tiles, while engines and machinery are mounted on vibration-dampening shock absorbers to minimise underwater noise. Although Pakistan originally intended to use German MTU diesel engines, Western export restrictions forced a switch to China’s CHD 620 engines. While these Chinese powerplants may require more frequent maintenance than their Western counterparts, they remain fully operational and do not fundamentally diminish the submarine’s combat effectiveness.

Nor are the Hangor boats merely difficult to detect. They are heavily armed. Six 533 mm torpedo tubes enable them to launch heavyweight torpedoes against surface ships and submarines alike, while Chinese anti-ship cruise missiles such as the YJ-18E or CM-708UNB provide a potent stand-off strike capability. Combined with advanced sonar suites, including towed-array sonar, electro-optical sensors and a Pakistani-developed combat management system, the class offers Pakistan a credible platform for sea denial and anti-access operations.

China’s motivations are not difficult to discern. Strengthening Pakistan’s underwater fleet helps secure sea lanes across the Arabian Sea and northern Indian Ocean while simultaneously stretching India’s naval resources. It also fits neatly into Beijing’s broader strategy of expanding influence across the Indo-Pacific through infrastructure investment, military cooperation and strategic partnerships.

Pakistan’s growing underwater fleet introduces greater uncertainty into Indian naval planning, particularly if Hangor-class submarines begin regular deployments into the Bay of Bengal. Such operations would complicate surveillance, threaten maritime trade routes during crises and demand a more persistent anti-submarine warfare posture from the Indian Navy.

Yet the more troubling story lies within India’s own procurement system. For well over a decade, India's conventional submarine modernisation has been characterised by indecision, procedural delays and bureaucratic caution. Project 75(I), conceived to build six next-generation conventional submarines equipped with Air-Independent Propulsion, has repeatedly slipped behind schedule. What should have been a timely replacement programme has instead become a case study in how strategic urgency can be overwhelmed by administrative complexity.

Several factors contributed to these delays. India’s insistence on acquiring a proven AIP system, while understandable given the sophistication of the technology, significantly lengthened the evaluation process. Successive rounds of technical assessments, commercial negotiations and stringent indigenous manufacturing requirements further prolonged decision-making. At the same time, limitations in domestic shipbuilding infrastructure, particularly in integrating new technologies at Mazagon Dock Shipbuilders Limited, slowed progress even further.

The result is a widening capability gap. Many of the Indian Navy’s Kilo-class submarines are approaching the limits of their operational lives, yet their replacements remain years away. Although the Union government has now cleared the approximately Rs. 70,000 crore Project 75(I), paving the way for a contract between Mazagon Dock Shipbuilders Limited and Germany’s Thyssenkrupp Marine Systems, the first submarine is unlikely to enter service before the early 2030s. Full induction of all six boats may not be completed until the latter half of that decade.

For the next seven or eight years, India's underwater fleet will continue to rely heavily on ageing conventional submarines, while regional competitors induct quieter and more capable platforms. Although the Indian Navy’s professionalism, network-centric operations and growing fleet of maritime patrol aircraft will help offset some disadvantages, technology cannot be indefinitely substituted by tactics alone.

Defence capability is determined not merely by budgets or industrial ambition but by the speed with which strategic decisions are translated into operational assets. In modern warfare, delays are themselves a strategic liability.

India retains considerable maritime advantages. Its navy remains larger, more experienced and increasingly integrated with like-minded partners across the Indo-Pacific. Indigenous nuclear-powered submarines are progressing steadily, and Project 75(I), once underway, will strengthen conventional underwater capabilities significantly.

But Pakistan’s Hangor-class submarines serve as a reminder that strategic competition rarely waits for procurement files to move.

(The writer is a retired naval aviation officer and a defence and geopolitical analyst. Views personal.)