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India's underwater nuclear deterrence is entering a critical phase with the impending induction of INS Aridhaman, the third Arihant-class nuclear-powered ballistic missile submarine, expected by May 2026. 

This development will see INS Arihant and INS Arighat joined by Aridhaman, forming a trio of indigenously built SSBNs under the Strategic Forces Command.

Amid China's vast submarine expansion across the Indo-Pacific and Pakistan's acquisition of advanced Chinese-origin vessels with air-independent propulsion, New Delhi is fortifying the sea-based leg of its nuclear triad—the most survivable element for assured retaliation.

INS Arihant, commissioned in August 2016, marked the fruition of the secretive Advanced Technology Vessel programme. Constructed at Visakhapatnam's Shipbuilding Centre, this 6,000-tonne submarine is powered by an 83 MW indigenous Compact Light Water Reactor. At 111.6 metres long, it achieves submerged speeds of about 24 knots, with endurance constrained mainly by crew provisions rather than fuel. Its armament includes four vertical launch tubes for up to 12 K-15 Sagarika missiles (750 km range) or four K-4 missiles (3,500 km range), plus six 533 mm torpedo tubes for defence.

Arihant's pivotal achievement came in 2018 with its first deterrence patrol, operationalising India's sea-based nuclear arm and completing the triad alongside land and air vectors. This patrol underscored the submarine's role in guaranteed second-strike capability, immune to pre-emptive strikes from beneath the ocean depths.

INS Arighat, commissioned on 29 August 2024, refines Arihant's design while maintaining the 6,000-tonne displacement. Built at the same Visakhapatnam facility, it features an enhanced pressurised light water reactor for prolonged stealthy operations.

Optimised for K-4 missiles, Arighat's four launch tubes extend India's strike envelope deeper into the Indian Ocean. It integrates indigenous sonars like USHUS and Panchendriya, alongside six torpedo tubes and advanced quieting for superior deterrence patrols.

With two SSBNs, India edges towards rotational patrols, mitigating downtime from maintenance and crew cycles that limit a single boat's availability. Arighat's refinements in systems and acoustics bolster sustained underwater presence.

INS Aridhaman elevates the class to 7,000 tons, incorporating eight vertical launch tubes for up to 24 K-15s or eight K-4s—and potentially future K-5 missiles with 6,000 km reach. Powered by an upgraded 83 MW reactor, it employs a seven-blade propeller, anechoic tiles, and sound-dampening for minimal acoustic signature. Submerged speeds match 24 knots, with expanded space for crew comfort, command systems, and enhanced sonars.

INS Aridhaman's scale enables continuous at-sea deterrence (CASD): with three boats, one can patrol while others refit or train. This triad ensures perpetual second-strike readiness from secure Indian Ocean bastions.

Operated from the secure Project Varsha base near Visakhapatnam—with underground pens for asset protection—the SSBNs anchor India's credible minimum deterrence doctrine. Unlike vulnerable land silos, submerged platforms offer unmatched survivability.

Complementing SSBNs, Chakra-III—an Akula-class nuclear attack submarine from Russia—is slated for 2027–28 induction. Focused on anti-ship, anti-submarine, and escort roles, it enhances tactical underwater dominance.

Parallel efforts include Project-75I: six diesel-electric submarines with air-independent propulsion (AIP) under an $8 billion programme. Based on Germany's Type-214 with fuel-cell AIP, these will be built at Mazagon Dock with technology transfer, replacing ageing fleets for covert surveillance and sea denial.

AIP grants extended submerged endurance without snorkelling, vital in contested waters. This bolsters conventional capabilities alongside strategic SSBNs.

CASD demands multiple submarines to cover refits and training. Aridhaman's missile capacity offers strike flexibility, with K-4 ranges allowing patrols from safer depths. Future K-5 integration could further evolve tactics.

India's doctrine prioritises assured retaliation over parity, targeting devastating response even post-first strike.

China fields over 50 diesel-electric and 10 nuclear submarines, including Jin-class SSBNs with JL missiles, projecting into the Indian Ocean. Pakistan inducts eight Chinese Yuan-class AIP boats for Arabian Sea denial, lacking nuclear-powered platforms.

India lags numerically but excels qualitatively against Pakistan via SSBNs and incoming Chakra III. Versus China, emphasis falls on stealth, endurance, and theatre-specific deterrence in the Indian Ocean.

This SSBN build-up shifts India's posture from incremental to robust, ensuring the nuclear triad's sea leg remains stealthy, resilient, and unassailable.

TOI