On Friday, India inducted its third nuclear-powered ballistic missile submarine (SSBN), INS Aridhaman, into the Indian Navy besides the advanced stealth frigate INS Taragiri at Visakhapatnam. While there is no official word yet on the commissioning of INS Aridhaman, Defence Minister Rajnath Singh, who was present at the two separate commissioning ceremonies, referred to the SSBN in a cryptic post on X, saying: “Not just words but power, ‘Aridhaman’!”

The quiet commissioning of INS Aridhaman, which will significantly strengthen India’s sea-based nuclear deterrent capabilities, is in line with how the previous two indigenous Arihant-class submarines, INS Arihant and INS Arighaat, were inducted in 2016 and 2024 respectively.

What the induction means

With Aridhaman’s induction, India will have three operational ballistic missile submarines at sea for the first time. This 7,000-tonne vessel is larger and technologically more advanced than its predecessors. Equipped with eight vertical launch tubes, it is designed to carry more long-range nuclear-tipped missiles than INS Arihant and INS Arighaat.

These missiles include the short-range K-15 submarine-launched ballistic missiles (SLBM) with a range of up to 750 km, and the longer-range K-4 nuclear-capable SLBMs that can hit targets 3,500 km away. Aridhaman’s capacity is twice that of Arihant: it can carry either eight K-4 missiles or up to 24 K-15 missiles.

Like the other two SSBNs, Aridhaman will be a key component of India’s nuclear triad. This refers to a country’s ability to launch nuclear missiles from platforms in the air, land, and at sea. Nuclear-capable missiles (such as the Agni series) can be launched from land, and fighter aircraft such as the Rafales, Su-30MKIs, and Mirage 2000s can deliver nuclear warheads.

Although India’s nuclear doctrine stipulates a “no first use” policy — it is committed to using nuclear weapons solely for deterrence and retaliation — SSBNs guarantee India’s second-strike capability. Should an adversary deliver a first nuclear strike on India’s land and air bases, an SSBN can launch a retaliatory nuclear attack, establishing deterrence.

India is part of a select group of countries with nuclear triad capabilities, which includes the US, Russia, China, and France. While the US operates 14 Ohio-class SSBNs and 53 fast-attack submarines, China has 12 nuclear submarines, including six nuclear-powered attack submarines.

Aridhaman’s induction was expected. In December 2025, Navy Chief Admiral Dinesh Tripathi had said that India’s third nuclear submarine was in the final stages of trials and would be commissioned soon.

India’s nuclear-powered submarine project was initiated more than three decades ago, involving both private firms and the Defence Research & Development Organisation, with help from Russia.

INS Arihant was launched in 2009, and commissioned into the Navy in 2016 as its first SSBN. It conducted its first deterrence patrol in 2018, establishing India’s nuclear triad. In October 2022, the Ministry of Defence announced that INS Arihant had successfully launched an SLBM “with very high accuracy” in the Bay of Bengal.

INS Arighaat is significantly more technologically advanced than INS Arihant, as its construction involved advanced design and manufacturing technology, detailed research and development, utilisation of special materials, complex engineering, and highly skilled workmanship, according to the Ministry of Defence.

Arighaat is armed with indigenously built K-15 missiles. Like Arihant, it is powered by 83 MW-pressurised light-water nuclear reactors, which allow it to remain submerged and undetected for much longer than conventional diesel-electric submarines.

What comes next

India’s fourth SSBN, codenamed S4* and also from the Arihant class, is currently under construction and just like Aridhaman, it will be able to carry more K-4 missiles due to its larger size. The Navy’s second-strike capability will be assured once S4* is commissioned, since at least one submarine can be on patrol at any given point of time even as the others undergo maintenance or are deployed elsewhere.

India is also pursuing a nuclear-powered attack submarine (SSN) programme. The Navy plans to build two SSNs indigenously and acquire one on lease from Russia, which is expected to arrive by 2027-28, bridging the capability gap until India’s own boats are ready.