Nuclear-Powered Ballistic Submarines (SSBN) and India’s Strategic Deterrence

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India recently launched its fourth nuclear-powered ballistic missile submarine (SSBN), S4*, which marks a significant step in the country's maritime defense capabilities. S4* is part of India’s Advanced Technology Vessel (ATV) programme and is larger than its predecessor, INS Arihant (S2). It is equipped with advanced weaponry, including the K-4 submarine-launched ballistic missile (SLBM) with a range of 3,500 kilometers. This marks a major enhancement of India's nuclear deterrence and second-strike capability.

India’s Fleet of Nuclear Submarines

India’s first three SSBNs include INS Arihant (S2), INS Arighaat (S3), and Aridhman (S4). While INS Arihant is already operational, INS Arighaat and Aridhman are at various stages of completion. The completion of Arihant’s first deterrence patrol in 2018 marked the successful establishment of India’s nuclear triad, which includes the capability to launch nuclear strikes from land, air, and sea.

India’s Nuclear Doctrine

India’s nuclear strategy is shaped by two key principles: Credible Minimum Deterrence (CMD) and a No First Use (NFU) policy. CMD focuses on maintaining a sufficient yet controlled nuclear arsenal that is powerful enough to deter adversaries without unnecessary expansion. The No First Use doctrine commits India to only use nuclear weapons in retaliation if first attacked with nuclear weapons.

The Advanced Technology Vessel (ATV) Project

India’s ATV project, initiated in the 1980s, aimed to develop indigenous nuclear-powered ballistic missile submarines. This project was a response to the strategic lessons learned after the 1971 Indo-Pakistani War, which emphasized the need for a robust nuclear deterrent. The project achieved its first milestone with the launch of INS Arihant, which marked the beginning of India’s indigenous nuclear submarine program.

Significance of SSBNs in India’s Defense Strategy

Nuclear-powered submarines, particularly SSBNs, play a crucial role in maintaining credible nuclear deterrence. These submarines, equipped with long-range ballistic missiles, enhance India’s second-strike capability, ensuring that the country can retaliate even if its land-based and air-based nuclear arsenals are compromised. The launch of S4* strengthens this deterrence posture and contributes to regional security stability.