P-75I is India's planned programme to acquire a new generation of advanced conventional submarines, building on the experience of the earlier Project-75. As a future project, its details are still being finalised, but its central aim is well established: to field diesel-electric attack submarines fitted with air-independent propulsion (AIP), giving them far greater underwater endurance than conventional boats. The programme is expected to involve construction in India with foreign design collaboration and significant technology transfer, and its specifics should be regarded as planned rather than settled.

Why air-independent propulsion matters

Conventional submarines must periodically come near the surface to run their diesel engines and recharge their batteries, a moment when they are most vulnerable to detection by radar, aircraft or other sensors. Air-independent propulsion allows a boat to generate power while remaining submerged for much longer, greatly reducing how often it must expose itself. This makes AIP-equipped submarines significantly harder to find and hold, narrowing the gap between conventional boats and far more expensive nuclear submarines for regional operations. For a navy operating in contested near seas, this extended submerged endurance is a decisive tactical advantage that can transform how a boat is employed.

P-75I is intended to succeed and complement the Kalvari-class boats delivered under Project-75. Where the Kalvari-class established modern submarine construction and quality processes in India, P-75I is expected to add AIP, greater indigenous content and more advanced weapons and sensors. The programme is planned to be executed largely at Indian yards such as Mazagon Dock Shipbuilders (MDL), sustaining and deepening the submarine-building ecosystem so that hard-won skills are not lost between projects.

Strategic context

India's underwater force is structured around two complementary elements. Nuclear-powered submarines such as the Arihant-class provide strategic deterrence and near-unlimited endurance, while conventional boats deliver cost-effective sea-denial and offensive capability in regional waters. P-75I sits firmly in the second category, intended to strengthen the conventional fleet as older submarines retire and as regional navies expand their own underwater arms. Maintaining an adequate number of capable submarines is a recognised priority, since these platforms take many years to design, build and bring into service and cannot be procured quickly in a crisis.

The programme is a priority for the Indian Navy, which has consistently emphasised the need to maintain submarine numbers and modern capabilities against a challenging maritime backdrop. Beyond the boats themselves, P-75I is expected to advance indigenous mastery of critical submarine technologies, including AIP systems, sonar, combat management and weapons integration, reflecting the self-reliance objectives that guide the Navy's warship and submarine programmes. Absorbing this technology domestically would reduce future dependence on foreign designers for one of the most sensitive categories of military hardware.

Because the programme is still being shaped, timelines, numbers, choice of foreign partner and final configurations remain subject to decision and negotiation, and should be treated as planned rather than fixed. Large, complex acquisitions of this kind typically involve extended evaluation and contracting phases before construction begins. What is clear is the strategic intent: to give India a fleet of quiet, enduring, largely home-built conventional submarines able to operate confidently across the Indian Ocean Region.

If realised as envisaged, P-75I would mark another important step in India's long journey toward designing and building its own submarines with steadily increasing indigenous content. In doing so it would reinforce the undersea leg of a balanced and modern naval force, complementing the strategic deterrent provided by nuclear boats with a strong, cost-effective conventional capability suited to the country's regional maritime challenges. The eventual induction of these boats would help offset the retirement of older vessels and keep the submarine arm at a credible strength, an outcome the Navy has long identified as essential to maintaining a favourable undersea balance in its primary area of interest.