India is moving closer to a major leap in underwater warfare capability with the long-anticipated Project-75I (P-75I), a strategic naval modernization program that will deliver six next-generation diesel-electric attack submarines in partnership with Germany’s thyssenkrupp Marine Systems and India’s Mazagon Dock Shipbuilders Limited. Valued at approximately ₹70,000 crore (about $8 billion), the program represents one of the most significant naval procurement efforts in India’s recent defence history.
According to defence sources familiar with the program, the initiative will produce the largest conventional submarines ever inducted into the Indian Navy, marking a decisive shift in the country’s undersea warfare posture amid intensifying maritime competition in the Indo-Pacific.
The submarines will be built under India’s flagship indigenous manufacturing framework, with all six vessels constructed domestically at MDL’s shipyard in Mumbai, while incorporating extensive German design expertise and technology transfer.
The acquisition under P-75I comes at a time when India is seeking to significantly enhance its deterrence and surveillance capabilities across the Indian Ocean Region (IOR). The growing operational tempo of the Chinese People’s Liberation Army Navy (PLAN), including deployments of nuclear and conventional submarines in waters near India’s maritime zones, has accelerated New Delhi’s push for quieter, longer-range, and more survivable underwater platforms.
The Indian Navy currently operates a mix of Russian-origin Sindhughosh-class submarine and French-origin Kalvari-class submarine. While these platforms have provided a credible conventional deterrent, naval planners have consistently emphasized the need for improved endurance, stealth, and firepower to match evolving regional threats.
The P-75I program is intended to fill that capability gap by introducing submarines with significantly greater submerged endurance, sensor sophistication, and weapons payload capacity.
At the heart of the program is a partnership with thyssenkrupp Marine Systems, which will provide the design foundation based on its advanced U-212CD submarine architecture.
However, Indian versions will not be direct exports. Defence sources describe them as heavily modified and enlarged variants, internally referred to as the “U-214NG” (Next Generation) configuration. While European navies such as Germany and the Netherlands are fielding standard U-212CD boats with submerged displacements of roughly 2,800 tons, the Indian variants are expected to be significantly larger, with estimates ranging from 3,400 to 3,500 tons submerged.
This expansion places them well above India’s current conventional submarine fleet in terms of size and endurance. For comparison, the Sindhughosh-class submarines displace just over 3,000 tons submerged, while the Kalvari-class boats are substantially smaller at around 1,700–1,800 tons.
The increase in hull volume is not merely structural; it is central to India’s operational requirements for extended-range patrols across vast maritime domains, from the Arabian Sea to the Bay of Bengal and deep into the western Pacific approaches.
One of the most critical features of the P-75I submarines will be the integration of a modern Air Independent Propulsion (AIP) system. This technology allows non-nuclear submarines to remain submerged for extended durations without surfacing or snorkeling, dramatically reducing their acoustic and radar detectability.
Combined with larger lithium-ion or advanced battery banks, the AIP system is expected to provide significantly improved submerged endurance compared to earlier Indian submarines. This capability is particularly important for operations in contested waters, where surfacing can expose submarines to surveillance by satellite, maritime patrol aircraft, or enemy surface combatants.
The expanded hull design also permits additional internal space for fuel reserves, crew accommodations, and mission-specific payloads, enabling longer deployments without resupply.
The enlarged platform will accommodate a more comprehensive suite of weapons and sensors than India’s existing conventional submarines. Defence sources indicate that the design will support heavier torpedoes, anti-ship missiles, and potentially land-attack cruise missiles, significantly expanding the submarine’s tactical flexibility.
A key enhancement is the inclusion of a vertical launch system (VLS), which would allow for rapid deployment of multiple missile types without relying solely on torpedo tubes. If fully realized, this capability would mark a notable shift in India’s conventional submarine strike doctrine, enabling deep-strike missions against maritime or coastal targets.
The sonar and electronic warfare suite is also expected to be substantially upgraded. The larger hull allows for the integration of extended flank arrays, improved passive sonar systems, and advanced towed array sensors, significantly enhancing detection range and stealth tracking capability.
In parallel, India plans to integrate indigenous combat management systems, reflecting its broader push toward defence electronics self-reliance.
A central pillar of the P-75I program is its emphasis on domestic production and technology absorption. Under the agreement with Mazagon Dock Shipbuilders Limited, all six submarines will be constructed in India, with a progressive increase in indigenous content.
Open-source defence estimates suggest that the first submarine will have approximately 45 percent indigenous components, gradually increasing to around 60 percent in later vessels. This phased localization strategy is intended to ensure that India develops a sustainable industrial ecosystem capable of supporting future submarine construction independently.
The transfer of technology arrangement with thyssenkrupp Marine Systems is expected to cover critical areas such as hull design, propulsion integration, stealth shaping, and systems engineering. Indian engineers will also gain access to advanced manufacturing processes, including modular construction techniques and precision hull welding standards.
Defence analysts note that this collaboration could become a cornerstone for India’s long-term submarine industrial base, reducing reliance on foreign suppliers for future undersea platforms.
The introduction of the P-75I submarines is widely seen as a response to evolving maritime dynamics in the Indo-Pacific. China’s expanding submarine fleet and increased presence in the Indian Ocean have raised concerns in New Delhi about underwater domain awareness and sea lane security.
With larger, quieter, and more capable submarines, India aims to strengthen its ability to conduct persistent surveillance, deny adversary access to strategic maritime zones, and secure critical shipping routes.
The Indian Ocean Region is increasingly viewed as a contested space, not only for military deployments but also for trade security, energy transit, and geopolitical influence. The P-75I program therefore carries significance beyond pure military modernization; it is also a signal of India’s intent to remain a dominant maritime power in its immediate neighborhood.
Strategic analysts also point out that enhanced submarine capability improves India’s deterrence posture by complicating adversary naval planning. A more survivable and dispersed submarine fleet increases uncertainty for potential adversaries, particularly in crisis scenarios.
While the program has progressed through multiple stages of evaluation and negotiation, final contract execution and construction timelines remain subject to formal approvals and detailed engineering finalization. Defence sources indicate that once the contract is signed, construction will proceed in phased batches, with the first submarine expected several years after keel-laying.
The complexity of integrating foreign design with indigenous manufacturing processes is expected to extend development timelines, but officials argue that the long-term strategic benefits outweigh the initial delays.
Once fully inducted, the six submarines will form a core element of India’s conventional undersea warfare capability for decades to come.
The P-75I initiative represents one of the most ambitious naval modernization efforts undertaken by India in recent years. Through its partnership with thyssenkrupp Marine Systems and domestic production by Mazagon Dock Shipbuilders Limited, India is seeking not only to acquire advanced submarines but also to build a durable indigenous submarine construction ecosystem.
With significantly larger hulls, advanced Air Independent Propulsion systems, expanded weapons capacity, and improved stealth features, the future fleet is expected to redefine India’s conventional undersea warfare capabilities.
In a maritime environment increasingly shaped by great-power competition, the P-75I submarines are poised to become a central pillar of India’s naval strategy, reinforcing deterrence, extending operational reach, and strengthening its position across the Indo-Pacific.
