New Delhi is preparing to acquire a nuclear-powered attack submarine from Russia, reinforcing its fleet of ballistic-missile-carrying vessels, and accelerating its domestic SSN (Ship, Submersible, Nuclear) programme.
This development represents one of the largest reinforcements of India’s sea-based strategic deterrent since the commissioning of INS Arihant, and it arrives just as
Russian President Vladimir Putin lands in New Delhi on Thursday for his first visit to India in four years, also a first since Moscow launched its full-scale invasion of Ukraine.
How a decade-long negotiation was finalised
India has moved closer to formalising the lease of a Russian nuclear-powered attack submarine
valued at around $2 billion after nearly ten years of intermittent negotiations, reported Bloomberg.
Discussions were delayed repeatedly due to disagreements over cost and technical adjustments, but Indian officials recently visited a Russian shipyard to review progress.
According to those familiar with the process, both sides have closed the pending gaps, paving the way for India to receive the vessel within approximately two years — though the complexities of such projects mean delays remain possible.
The timing is significant as New Delhi has simultaneously been expanding its diplomatic engagement with Russia and China while attempting to manage tensions with the United States following punitive import tariffs introduced by US President Donald Trump.
Those duties — set at 50 per cent — have been part of Washington’s pressure campaign to curb India’s purchases of Russian energy.
In a Truth Social post in July, Trump noted, “They have bought vast majority of their military equipment from Russia and are Russia’s largest buyer of energy with China,” and Washington later imposed a 25 per cent “secondary tariff” on select Indian products.
Despite this pressure, India has maintained steady defence ties with Russia, especially in specialised areas such as nuclear propulsion where very few countries possess the expertise or willingness to collaborate.
The submarine, which will be leased for 10 years, cannot be used in combat due to the terms of the agreement. Its primary purpose will be to train sailors, refine nuclear-submarine operations and tactics, and support the Navy as India transitions toward its own domestically built attack submarines.
The arrangement mirrors earlier leases: a previous Russian vessel operated in Indian service for a decade before being returned in 2021.
Notably, only a handful of nations — the United States, United Kingdom, France, China and Russia — have the industrial and technological foundation required to operate nuclear-powered submarines.
Australia is attempting to join this circle under the AUKUS partnership, and South Korea has been exploring similar cooperation with Washington.
India remains one of the few countries with an indigenous nuclear submarine programme underway.
How India is also preparing to commission its third SSBN
Parallel to the submarine lease, India’s ballistic-missile submarine programme is approaching a key milestone: the third SSBN (Ship Submersible Ballistic Nuclear),
to be commissioned as INS Aridhaman, is nearly ready for induction.
Navy Chief Admiral Dinesh K Tripathi confirmed that the vessel is in “the final stages of trials and will be commissioned soon” on Tuesday.
This platform is larger than the first two SSBNs and will be able to carry more long-range ballistic missiles, significantly expanding India’s nuclear payload options at sea.
The INS Aridhaman, along with the forthcoming 7,000-tonne fourth SSBN (codenamed S-4), is designed to strengthen the survivability and persistence of India’s retaliatory nuclear capability under the country’s no-first-use doctrine.
The S-4 is projected to join the fleet around 2027, reported the Times of India.
India’s first two SSBNs — the 6,000-tonne INS Arihant (operational since 2018) and INS Arighaat (operational since 2024) — form the backbone of the sea-based nuclear deterrent.
The newer submarines are designed to carry a larger complement of K-4 ballistic missiles with a range of 3,500 km, effectively doubling the missile load of INS Arighaat.
The K-4 is also undergoing validation, with another test planned after an earlier one did not meet all required benchmarks.
India is additionally developing longer-range platforms such as the K-5 and K-6, expected to extend strike ranges to 5,000-6,000 km, putting large parts of the Indo-Pacific and China’s interior within reach.
Over the long term, India plans to design and construct larger SSBNs — around 13,500 tonnes — with more powerful nuclear reactors.
Ballistic-missile submarines are considered the most secure component of a nuclear triad due to their stealth and persistence underwater, capable of staying submerged for months.
With land-based Agni missiles and air-delivered nuclear weapons already in place, India’s strengthening of its SSBN fleet consolidates its position as a country with a complete and increasingly credible triad.
How India is modernising its Akula-class submarines
The centrepiece of India’s next-generation attack submarine capability will be the Akula-class submarine K-391 “Bratsk,” which is undergoing an extensive modernisation programme in Russia.
The overhaul, described as a “deep modernisation” rather than a routine refit, is being executed to the advanced 971M (Akula-4) standard. This makes it significantly more capable than previous Indian-leased submarines.
The programme, part of an intergovernmental agreement signed in 2021 and valued at roughly $3 billion, includes the upgrading of virtually every onboard system. The work is being conducted at the Zvezdochka Shipyard in Severodvinsk and has been in progress since 2023.
Enhancements cover the submarine’s navigation suite, combat management system, hydroacoustic arrays, periscopes, electronic warfare systems, and propulsion.
The primary power plant is being refurbished around the VM-4SG reactor, which produces 190 MW of thermal power.
Once overhaul trials in the Barents Sea conclude — expected toward late 2026 or mid-2027 — the vessel will undergo custom modifications tailored for Indian operational requirements.
Delivery to India is anticipated between late 2027 and early 2028, with the submarine to be rechristened INS Chakra III.
One of the defining upgrades will be its compatibility with the Indo-Russian BrahMos cruise missile in its extended 800-kilometre range form. The integration of BrahMos into 533-mm torpedo tubes will enable India to conduct precision strikes on land or sea targets from submerged positions.
This capability significantly broadens India’s strategic and conventional options across the Arabian Sea, Bay of Bengal, and into contested expanses of the South China Sea.
The submarine will also be equipped to operate India’s indigenous heavyweight torpedoes such as the Advanced Experimental Torpedo (AET), furthering India’s intent to diversify from dependency on Russian underwater munitions.
Improved sonar arrays — including a modern cylindrical bow array capable of detecting targets at longer ranges, the Skat-3 intercept suite, and a refined towed array sonar — will dramatically boost detection and tracking performance.
Data will be fused through the upgraded Omnibus-E combat information system, leveraging inputs from both acoustic and non-acoustic sensors.
Physically, the submarine displaces 8,140 tonnes when submerged, spans 110 metres, and can remain at sea for up to 100 days.
Powered by twin steam turbines capable of delivering underwater speeds up to 43 knots, the vessel is built for long-endurance patrols that can extend across 10,000 nautical miles — sufficient to monitor maritime corridors from the eastern coast of Africa to the Western Pacific.
Its weapons suite will include a mix of torpedoes and cruise missiles across ten tubes — six of 533 mm and four of 650 mm.
The torpedo inventory will include the UGST-M thermal torpedo and the UET-1 electric torpedo, along with Kalibr cruise missiles for anti-ship and land targets. Defensive tools include MG-74 Korund decoys and MG-104 noisemakers.
Enhanced acoustic quieting features — such as advanced pump-jet propulsion, sound-dampening mounts, and modern anechoic coatings — are designed to reduce the submarine’s noise signature by more than 10 decibels.
This places it among the quieter submarines of its class, approaching the acoustic performance of early Russian Yasen-class vessels.
Why nuclear submarines are a game-changer for India
Nuclear submarines offer decisive advantages over diesel-electric submarines, which India currently fields in significant numbers.
Nuclear propulsion enables submarines to remain submerged for extended periods without surfacing for air, making them harder to detect and capable of longer patrols. They also have larger hulls, which allow them to carry more weapons, sensors, and fuel.
India presently operates 17 diesel-electric submarines, but nuclear-powered vessels are essential for credible deterrence missions and long-range patrols across the Indian Ocean Region.
From monitoring choke points near the Strait of Hormuz to tracking surface groups in the South China Sea, nuclear submarines offer unmatched operational flexibility.
India’s long-term challenge remains the expanding undersea forces of its neighbours. China operates six Jin-class SSBNs armed with JL-3 missiles and is rapidly expanding its fleet. Beijing also fields six SSNs.
The United States maintains one of the world’s largest fleets with 14 Ohio-class SSBNs and more than 50 SSNs.
Russia continues to innovate with the Yasen-M, featuring next-generation sonar, advanced non-acoustic tools, and lithium-ion battery systems.
With China expanding its footprint across the Indian Ocean and tightening military coordination with Pakistan, India’s upgraded undersea capabilities function not only as deterrence but also as a counterweight in a region where strategic competition is heating.
Even as India relies on leased Russian platforms, its indigenous SSN project is progressing under a plan approved in 2024 at a cost of ₹40,000 crore.
Tripathi stated that the project is “proceedings as per plans.” This initiative envisions two domestically built attack submarines, each around 9,800 tonnes and powered by a 190 MW pressurized light-water reactor.
The first Indian-built SSN is expected to enter service by 2036-37, with the second following a few years later. The vessels will complement the Russian-origin INS Chakra III but eventually form the backbone of India’s undersea warfare capability.
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With inputs from agencies
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