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India Expands its Sea-Based Nuclear Deterrence with Commissioning of INS Aridhaman Submarine.
India continues to enhance its strategic deterrence capability with the integration of its third nuclear-powered ballistic missile submarine (SSBN), INS Aridhaman (S4), which is expected to enter service this year after nearly three years of trials. Currently, the Indian Navy operates two SSBNs, INS Arihant and INS Arighat, and this new addition will mark a significant step in the expansion of its strategic submarine fleet.

INS Arihant, India’s first indigenously built SSBN, was commissioned in August 2016. (Picture source: Indian MoD)
INS Arihant, India’s first indigenously built SSBN, was commissioned in August 2016. With a displacement of 6,000 tons, it is powered by an 83 MW pressurized water reactor using enriched uranium. Its induction was a critical milestone, enabling India to establish a credible sea-based nuclear deterrent. Its successor, INS Arighat, was commissioned in August 2024. While retaining the core design of INS Arihant, it incorporates several technological improvements, including enhanced sonar, navigation, stealth capabilities, and fire control systems, making it a more capable platform.
INS Aridhaman (S4), the third SSBN in the series, is in its final testing phase and is expected to join the fleet soon. Based on the design of INS Arihant and INS Arighat, it retains the 83 MW reactor but includes multiple technical upgrades derived from operational feedback. According to experts, it features advanced maintenance and safety enhancements to improve reliability and crew efficiency.
India's maritime deterrence strategy is driven by the need to counter potential threats in the Indian Ocean. Given the vulnerability of aircraft carriers to long-range ballistic missiles such as China’s Dong Feng-21 and Dong Feng-26, the Indian government has prioritized the development of nuclear-powered attack and ballistic missile submarines over acquiring a third aircraft carrier. In this context, the Cabinet Committee on Security (CCS) recently approved the construction of two nuclear-powered attack submarines to reinforce India’s presence in the Indo-Pacific region.
Meanwhile, the Indian Navy continues its conventional submarine program with the upcoming commissioning of the sixth Kalvari-class submarine, INS Vagsheer, scheduled for December 2024. Additionally, the construction of three new diesel-attack submarines will commence in collaboration with the French Naval Group to further enhance India’s conventional underwater capabilities.
With an increasing presence of Chinese warships in the Indian Ocean—averaging around ten PLA Navy vessels per month—and the anticipated deployment of long-range carrier-based patrols by 2025-26, India is accelerating its naval modernization efforts to safeguard its strategic interests. The integration of new SSBNs and attack submarines underscores New Delhi’s commitment to maintaining a credible deterrence posture and ensuring maritime security in the region.