By N. C. Bipindra

New Delhi: India, on April 3, 2026, commissioned the third nuclear-armed submarine, INS Aridhaman, codenamed S4, at the Submarine Building Centre in Visakhapatnam, signalling to its archrivals China and Pakistan its growing second-strike capabilities.

Defence Minister Rajnath Singh attended the brief ceremony to mark the induction of INS Aridhaman into the Strategic Forces Command, the tri-services arm with the trigger for all Indian nuclear weapons.

The induction of INS Ardhaman strengthens India’s nuclear triad, the capability to fire nuclear-armed missiles from land, air, and underwater. The underwater nuclear capability is the most potent due to the surprise element it brings to the Indian arsenal.

According to Ministry of Defence officials, the INS Aridhaman commissioning was not a public event due to the secrecy connected to the strategic weapons platform project.

However, Rajnath Singh dropped a cryptic clue on the submarine’s induction when he posted on X: “It’s not words but power, ‘Aridhaman’!”

Indian media reports had in January 2025 speculated on the INS Aridhaman commissioning by April 2025 after the vessel had ventured into the sea for its extensive trials.

INS Aridhaman is the third of the four-submarine project, initially codenamed Advanced Technology Vessel, or ATV. The first vessel, INS Arihant, was commissioned in 2016, followed by the second vessel, INS Arighaat, in August 2024.

A fourth vessel, tentatively christened ‘Arisudan’ and codenamed S4*, is going through trials at present and is likely to be commissioned next year.

While INS Arihant and INS Arighaat are smaller, 6,000-tonne vessels, INS Aridhaman and ‘Arisudan’ are larger, 7,000-tonne submarines.

These two vessels carry more firepower than the first two of the Arihant-class submarines, with the capability to carry 24 750-km-range K-15 Sagarika missiles and eight K-4 3,500-km-range nuke-tipped missiles. Arihant and Arighaat are armed with 12 Sagarika or four K-4 missiles.

In December 2025, Indian Navy chief Admiral Dinesh Tripathi had noted that Aridhaman was in the final phase of its trials and scheduled for commissioning at the earliest.

Globally, the US, Russia, China, and France are the other four in an elite club of nations that build and operate SSBN (Ship Submersible Ballistic Nuclear), which is navalese for nuclear-armed submarines.

Apart from the SSBNs, India also plans to build at least six nuclear-powered submarines, or SSN, under a project approved by Prime Minister Narendra Modi-headed Cabinet Committee on Security (CCS).

The CCS has given the go-ahead for building two SSNs, of which one is to be commissioned by 2037 and the other by 2029. The SSNs are part of an amended 30-year submarine building plan of the Indian Navy approved in 1999, under which 24 conventional submarines were to be built by 2030.

However, only six conventional submarines, under Project 75, have been built and inducted till now. The Scorpene submarines were built at the Mazagon Docks and Shipbuilders Limited (MDL) with technical help from the French Naval Group.

The second batch of six conventional submarines, under Project 75(I), is in the final stages of a tendering process under which MDL is set to build advanced, next-generation submarines for the Indian Navy with help from the German ThyssenKrupp Marine Systems (TKMS).

Project 75(I) submarines would be equipped with an Air Independent Propulsion (AIP) system, enabling them to stay submerged underwater for longer periods.

Project 75(I) was to be followed by a Project 76, under which another 12 conventional diesel-electric-powered submarines would be built.

But, when later Manohar Parrikar was India’s Defence Minister, the Modi government changed the plan to build six nuclear-powered submarines instead of the 12-vessel plan.

India’s defence budget funds the nuclear-armed submarines programme separately under the capital expenditure head, and not under the naval capital budget.

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