The commissioning of INS Aridhaman on 3 April at the Ship Building Centre in Visakhapatnam marks a decisive milestone in India’s nuclear deterrence posture. With this third nuclear ballistic missile submarine now operational, India has achieved the critical threshold required to sustain a continuous at-sea deterrent.

The event was conducted without formal announcement, though Defence Minister Rajnath Singh posted a message in Hindi that Carnegie India translates as “Not words but power, Aridhaman.” Singh was in Visakhapatnam at the time for the commissioning of a separate naval vessel, the fourth frigate under the Project-17A program.

India’s nuclear doctrine, announced in 2003, is founded on a no-first-use policy and an assured retaliatory second-strike capability. Maintaining a continuous deployment at sea requires at least three SSBNs: one on patrol, with the others undergoing maintenance or transit.

With INS Aridhaman joining INS Arihant and INS Arighaat, India has now reached this strategic threshold. The Arihant, developed under the Advanced Technology Vessel programme, was launched in 2009 and commissioned in 2016, later completing its first deterrence patrol in 2018.

The Arighaat followed in August 2024, and the Aridhaman, with further classified technological enhancements, completes the triad’s sea leg.

India’s nuclear arsenal includes the Prithvi and Agni series of ballistic missiles. The Agni-5, with a range exceeding 5,000 km, is cannisterised for mobility and storage, and was tested in 2024 with multiple independently targetable re-entry vehicles.

Air-delivered nuclear capability is provided by Mirage-2000, Sukhoi-30MKI and Rafale aircraft. Among the triad, SSBNs remain the most survivable platform for second-strike capability, a fact underscored by the practices of all five recognised nuclear powers, each of which operates SSBNs armed with intercontinental submarine-launched ballistic missiles.

India, however, faces a capability gap in this area. Its current SSBNs are armed with the K-15 missile, with a limited range of 750 km, necessitating deployment close to adversary coastlines for effective retaliation.

The Arighaat and Aridhaman are capable of carrying the K-4 missile, with a range of 3,500 km, though this system is not yet fully operational. Once deployed, the K-4 is expected to form the backbone of India’s underwater deterrent until the K-5, with a planned range of 5,000 km, enters service.

A fourth submarine, designated S4*, was launched in 2024 and is expected to be commissioned next year. Future platforms include the larger S5 class, projected at around 13,500 tonnes and powered by more advanced reactors.

Attention is also turning to nuclear-powered attack submarines (SSNs), seen as vital for long-range endurance operations in the Indian Ocean. India currently operates 17 conventional submarines, most nearing the end of their service lives. In 2024, the Cabinet Committee on Security approved the design and construction of two SSNs, though the first is not expected to enter service until 2036–37.

The strategic context is shaped by China’s naval expansion. Beijing operates more than 60 submarines, including at least 12 nuclear-powered vessels.

According to the US Office of Naval Intelligence, by 2035 half of China’s projected fleet of around 80 attack submarines could be nuclear-powered. This trajectory underscores the long-term challenge India faces in sustaining credible deterrence and countering regional imbalances in undersea warfare capabilities.

IDN (With Agency Inputs)