India's evolving strategic posture in the Indian Ocean is increasingly shaped by Continuous at Sea Deterrence, which seeks to ensure the permanent deployment of at least one nuclear-armed ballistic missile submarine (SSBN) for an assured second-strike capability. While India promotes this development as part of "credible minimum deterrence", the expansion of its nuclear capabilities suggests a shift toward a more assertive and potentially escalatory counterforce posture. This transformation has significant implications for global strategic stability within the complex security matrix of South Asia.

India's SSBN programme was formally launched under the ATV project, with collaboration between the Indian Navy, the Bhabha Atomic Research Centre, and the Defence Research and Development Organisation. The commissioning of INS Arihant in 2016 and its first operational patrol in 2018 marked India's entry into the exclusive club of nuclear triad powers. Since then, the programme has accelerated rapidly. INS Arighat was commissioned in August 2024, and the S4 and S4* SSBNs are undergoing sea trials with operational status expected by 2025-26. Additionally, India is developing a new S5-class, expected to displace 13,500 tons, signaling the shift to a more survivable and capable platform.

These submarines are being paired with India's K-series submarine-launched ballistic missiles (SLBMs). While the K-15 (750-1,500 km) is already in service, the K-4 (3,500-4,000 km) has been tested and is nearing deployment. Furthermore, the K-5 SLBM, reportedly has a range exceeding 5,000 km and equipped with Multiple Independently Targetable Reentry Vehicles (MIRVs), followed by the K-6 hypersonic missile with 8,000 km range, which is under development. These MIRV-capable SLBMs would enhance........

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