In 1997, theCabinet Committee on Security (CCS) - the highest-decision making body of India'sMinistry of Defence (MoD), approved the construction of twoType 209/1500 attack submarines (SSK) at a then-estimated cost ofINR ₹700 crore. This effort, which was conceived in the wake of aninternational corruption scandal related to India's acquisition of theShishumar-class submarines, called for the construction of two Type 209/1500 SSKs atMazagon Dock Shipbuilders Limited (MDL) with the assistance of a foreign naval firm in a corroborative role. In accordance with the scheme, theIndian Navy (IN) and MDL approached several naval enterprises for assistance; however, the French-basedThomson-CSF (TCSF) was the only firm willing to participate.^[2]

Two years later, on 12 July 1999, theCabinet Committee on Security (CCS) approved a two-phase plan to build 24 submarines over a span of 30 years.^[3][4] The plan was named 'Project for Series Construction of Submarines for the Indian Navy and Acquisition of National Competence in Submarine Building', also referred as 'Submarine-building Perspective Plan'. For the first phase, six submarines each were to be built at MDL underProject 75 (P-75) along with a parallelproduction line of another public/private shipyard^[5] underProject-75 (India) or P-75(I) withtechnology transfer. Under the second phase, twelve submarines would be built including complete indigenous design, development and construction of submarines in India.^[2][6] While the first phase was scheduled for completion within 2012, the second phase would be executed in 2012–2030.^[7]

For theProject-75, two options emerged. The first being construction of the Type 209/1500 at MDL initially with the combat suite of TCSF with the rest being based onmodifiedScorpène submarine design based on Naval requirements. The second option recommended the construction of all the SSKs based on the newerScorpène design. Ultimately, the Naval Heqadquarters chose the latter, reasoning that theScorpène, which had been offered with a provision oftechnology transfer (TOT), was more advanced than the Type 209/1500. The initial plan to ally with TCSF was dropped in April 2001 and negotiations for the procurement of theScorpène design under the first phase, dubbed Project-75 (P-75), began in November 2001. TheScorpène design was offered by another French-based naval firm, Armaris (laterDCNS, nowNaval Group).^[2] The P-75 contract signed on 6 October 2005^[8] resulted in the construction of sixKalvari-class submarines^[6] beginning 23 May 2009.^[9] The final unit,INS Vagsheer (S26), was commissioned in January 2025.^[10]

Though the second batch of six submarines, underProject-75 (India), was to be executed simultaneously alongside P-75, financial constraints within the MoD led to P-75 being the only project sanctioned for six submarines.^[11] Proposals to move ahead with the acquisition failed twice after theproject was approved in 2010 and 2014.^[12][13] Following delays, the Navy mandated the presence of an operationalair-independent propulsion (AIP) plant with the submarine design. This was done to maintain the submarine's relevance in future as the boats' induction timeline was already delayed to 2022.^[13][14] The third approval from the Defence Acquisition Council (DAC), chaired by theIndian Minister of Defence, was accorded in January 2019.^[15][16] In January 2025, the bid byLarsen & Toubro to buildS-80 Plus-classsubmarine, in collaboration with Spain'sNavantia, was disqualified.^[17][18] Mazagon Dock's partnership withTKMS remained the only bidder who were thereafter invited for techno-commercial negotiations with the Indian Ministry of Defence.^[19] Negotiations were reported to have begun in July 2025^[20] while the deal could be signed in January 2026.^[21][22]

The second phase of the plan was amended midway to maintain the relevance of the submarine fleets as per evolving threats.^[7] The program to construct and deploy a fleet of nuclear submarines was first envisaged in late 1990s was fast-tracked following growingpatrols by thePeople's Liberation Army Navy ships. This included a solitary two-month "anti-piracy" patrol by aType 093 submarine in theIndian Ocean before returning toYulin Naval Base on 13 December 2013. On 12 February 2014, R&AW evaluations described the deployment as having significantly intensified India’s security concerns.^[23] The Navy has already acquired experience of operatingnuclear submarines after leasing ofINS Chakra (1987) andINS Chakra (2011) for three and nine years, respectively.^[24][25][26] The force has also ordered athirdChakra submarine for a lease of 10 years starting 2025.^[27][28] The submarine is expected to be delivered to India in 2028 following delays.^[29][30]

In February 2015, theGovernment of India through aCabinet Committee on Security (CCS) approval, gave rise to another indigenous submarine project — theProject 75 Alpha (now Project 77). A fleet of sixnuclear attack submarines, with a displacement of 6,000 tonnes, were to be built under the project.^[31] The design phase had begun by December 2017^[32] with constructions to commence by 2023–24 and first unit to enter service in 2032.^[33] The preliminary design phase was completed by February 2020.^[34] In October 2024, the CCS cleared the construction of first two units in the Shipbuilding Centre (SBC),Visakhapatnam, of the Ministry of Defence where theArihant-classsubmarines were built.^[35] The displacement was increased to 9,800 tonnes^[36] and equipped with 200MWe-ratednuclear reactor.^[37]

With the approval of the Project 77, the number of boats underProject-76 was reduced to six units. The design was expected to inherit elements from the Project-75 and Project-75(I) designs.^[7] The development was cleared by defence ministry in June 2024 followed by a feasibility study conducted byDRDO.^[38] An approval from theCabinet Committee on Security (CCS) for the further detailed design of the submarine is due as of February 2025.^[39]

Both Project 76 and Project 77 are being led by theAdvanced Technology Vessel headquarters which is responsible for the development and construction of India'snuclear-powered,ballistic missile submarine fleet includingArihant class andS5-classsubmarines.^[38][23] While the final two submarines from theArihant class is expected to be commissioned in early 2026 and 2027, respectively, the construction of first two units of S5 submarines has also begun in the Shipbuilding Centre (SBC),Visakhapatnam.^[40][41][42]