India's quest for a credible second-strike nuclear capability hinges on its burgeoning fleet of nuclear-powered ballistic missile submarines, known as SSBNs. Hidden deep underwater, these vessels form the cornerstone of the nation's No First Use doctrine, ensuring retaliatory strikes can inflict massive and unacceptable damage on any aggressor.

Recent unacknowledged tests of the K-4 submarine-launched ballistic missile underscore steady progress in this strategic domain.

India's 2003 Nuclear Doctrine explicitly pledges No First Use, positioning the country alongside China as one of only two nuclear powers with this commitment.

This policy mandates retaliation only after suffering a nuclear, biological, or chemical attack, emphasising massive second-strike responses. For such deterrence to hold, survivable platforms like SSBNs prove essential, evading satellite detection and radar tracking that plague land-based or air-delivered systems.

SSBNs represent the ultimate stealth predators, powered by reactors that sustain indefinite submersion limited only by crew endurance and provisions. India's Arihant-class submarines exemplify this capability, with INS Arihant commissioned in 2016 and INS Arighaat joining in August 2024 after extensive trials. Both displace around 6,000 tons and operate under the Strategic Forces Command.

A pivotal milestone occurred on 23 December 2025, when sources confirmed a successful K-4 SLBM test launch from INS Arighaat off Visakhapatnam in the Bay of Bengal. This marked the second such submarine-based firing, following a late-2024 test, with no official Ministry of Defence statement issued.

The solid-fuel K-4 boasts a 3,500-4,000 km range, enabling strikes across Pakistan and deep into China from secure Bay of Bengal waters.

Earlier iterations faced range constraints; INS Arihant initially carried the K-15 Sagarika SLBM with a mere 750-1,500 km reach, necessitating risky proximity to hostile shores. The K-4 alleviates this 'range anxiety', allowing submarines to remain protected by surface fleets and patrol aircraft while holding high-value targets at risk. Arihant-class boats accommodate four K-4s or twelve K-15s, or a mix thereof.

The program continues to expand, with INS Aridhaman—the third Arihant-class vessel—nearing commissioning in early 2026 after sea trials, as announced by Navy Chief Admiral Dinesh K Tripathi on 2 December 2025.

A fourth unnamed SSBN follows, completing a quartet that ensures perpetual at-sea deterrence: one on patrol, one in transit, one in refit, and one in reserve. Stretch variants with extended hulls will carry eight K-4s or twenty-four K-15s.

Looking ahead, the Defence Research and Development Organisation advances longer-range missiles under the K-series, named after former President APJ Abdul Kalam. The K-5 promises 5,000-6,000 km reach, while the MIRV-capable K-6 targets 8,000-9,000 km, both requiring larger S5-class submarines twice the Arihant-class size. These 'boomers' will align India with US and Russian capabilities, arming future platforms akin to global strategic giants.

India's Advanced Technology Vessel project, spanning decades, has overcome engineering hurdles like miniaturised reactors and missile integration. The recent K-4 tests from actual submarines—beyond prior pontoon firings—validate operational readiness, rendering shorter-range K-15s increasingly obsolete for strategic missions. This underwater triad leg completes India's nuclear deterrence posture alongside land and air vectors.

Strategic implications extend regionally, bolstering credibility against neighbours amid evolving threats. Four operational SSBNs will guarantee one always prowls silently, embodying the doctrine's promise of assured retaliation. As these 'slayers' and 'destroyers' multiply, India's submerged nuclear guarantee grows unassailable, deterring first strikes through inescapable consequences.

Based On IT Report