Just before he commissioned INS taragiri, India’s new stealth naval frigate, Defence Minister Rajnath Singh posted a terse and cryptic message on his social media handle - “it’s not a word, it’s power, it’s Aridhaman” – throwing the spotlight on India’s steadily advancing nuclear submarine programme, a cornerstone of its strategic deterrence architecture in an era of missile and drone strikes.
INS Arighat, India’s third nuclear-powered ballistic missile submarine (SSBN), is currently undergoing sea trials and the post was read by naval analysts that the tests “have been totally successful.”
At the heart of this effort lies the Advanced Technology Vessel (ATV) project, under which India is building a fleet of nuclear-powered ballistic missile submarines (SSBNs) designed to ensure a credible second-strike capability.
India currently operates two SSBNs -- INS Arihant, commissioned in 2016, and INS Arighaat, inducted in August 2024. The Arihant, the lead boat of this programme, completed its first deterrent patrol in 2018, marking India’s entry into an elite group of nations with operational nuclear triads.
INS Aridhaman (which is codenamed S4 project), is a larger and more capable successor, is expected to be formally commissioned in the coming weeks. It will be equipped with both K-15 short-range and K-4 intermediate-range submarine-launched ballistic missiles (SLBMs), with a range of 3,500 kms, significantly extending India’s reach.
A fourth boat, believed to be named INS Arisudan, codenamed S4 asterix, has already been launched and is also undergoing trials, with induction likely by early 2027.
The stealth frigate launched today by Singh at Vishakhapatnam, is a Nilgiri class missile frigate built at Mazagon docks.Construction of the ship began 2020 and it was launched in 2022 and its commissioning after extensive sea trials is seen as a milestone. The 7,000-tonne ship, equipped with BrahMos and other missiles, is expected to lend heft to India’s naval presence in the oceans where India operates.
“The two new nuclear submarines which are yet to be commissioned are part of what is considered a crucial evolutionary step, which we call the “Arihant-stretch” variants, will bridge the gap between the original Arihant-class and the more ambitious next-generation platforms,” said senior defence ministry officials.
With displacement estimated between 7,000 and 11,000 tonnes and improved nuclear reactors, the new boats offer greater endurance, stealth, and strike capability.
“These projects also mark a leap in indigenisation, with roughly 75 per cent of components sourced domestically, a key objective of India’s defence industrial policy,” said officials.
Beyond the Arihant line, India is already planning its next leap, which sources said will be the S5-class SSBNs. These will be significantly larger submarines, with displacement of around 13,500 tonnes and will reportedly carry up to 16 missiles, including longer-range K-5 and K-6 SLBMs with potential ranges of 5,000–8,000 km.
Construction is expected to begin around 2027, with the first induction likely in the early 2030s. These platforms would give India a true intercontinental sea-based deterrent, enhancing its ability to target adversaries deep within their territory.
In parallel, India is pursuing a fleet of nuclear-powered attack submarines (SSNs) under Project-77, with plans for six indigenous boats by the 2030s. Unlike SSBNs, which are designed for strategic deterrence, SSNs are geared toward hunting enemy submarines and protecting naval assets.
“The expansion of the submarine fleet is central to India’s nuclear triad and will give India the ability to deliver nuclear weapons from land, air, and sea,” said officials.
Of these, the sea-based leg is considered the most survivable, ensuring retaliation capability even after a first strike.
“This also aligns with India’s stated ‘No-First-Use’ doctrine, which relies on credible second-strike capability to deter nuclear aggression,” pointed out officials.
Strategically, the submarines also reinforce India’s posture in the Indo-Pacific, particularly in the context of China’s growing naval presence. With longer-range SLBMs, Indian SSBNs operating in the Indian Ocean can hold high-value targets at risk without leaving relatively safe waters.
