India’s recent successful test of the K-4 Submarine-Launched Ballistic Missile (SLBM) represents a pivotal advancement in the nation’s nuclear deterrence posture.

With a reported range of 3,500 kilometres, this missile equips India’s submarines to operate from relatively secure waters while maintaining the capability to strike high-value targets across Pakistan and significant portions of China. 

This development underscores India’s commitment to bolstering its sea-based nuclear triad, enhancing strategic credibility in a volatile regional landscape.

Rear Admiral Sudarshan Shrikhande (Retd), a former head of Naval Intelligence, has emphasised that the sea-based nuclear element of India’s deterrence architecture is rapidly approaching full operational readiness.

The K-4 test forms a critical component of this progress, validating the integration of advanced SLBM technology into the Indian Navy’s arsenal. His insights highlight how this milestone fortifies India’s ability to project power discreetly from the depths of the ocean.

The impetus for India’s pursuit of a sea-based nuclear deterrent traces back decades, catalysed primarily by China’s first nuclear test in 1964. This event profoundly shaped India’s strategic calculus, compelling the nation to develop a comprehensive nuclear triad comprising land, air, and sea-based delivery systems. Rear Admiral Shrikhande notes that China’s early nuclearization exposed India’s vulnerabilities, driving the long-term imperative for survivable second-strike capabilities.

India’s Arihant-class submarines, the cornerstone of its SSBN (nuclear-powered ballistic missile submarine) fleet, are central to this strategy. With two SSBNs already commissioned and a third, along with possibly a fourth, nearing readiness, the Navy is poised to achieve Continuous At-Sea Deterrent (CASD). This doctrine ensures that at least one submarine remains submerged and on patrol at all times, rendering a disarming first strike by adversaries exceedingly difficult.

The K-4 missile itself is a technological marvel, featuring solid-propellant propulsion for rapid launch readiness and advanced guidance systems for precision targeting. Capable of carrying nuclear warheads, it extends the reach of India’s underwater fleet far beyond coastal confines, allowing operations in the Bay of Bengal or Arabian Sea bastions. Successful tests from submerged platforms, including recent trials from INS Arihant, demonstrate maturity in cannisterised launch technology.

Pakistan’s response to the K-4 test has been marked by alarmist rhetoric, with narratives claiming it disrupts South Asia’s nuclear equilibrium. Such commentary, according to Rear Admiral Shrikhande, serves primarily to rationalise Pakistan’s escalating military expenditures and force modernisation programmes. He attributes this sabre-rattling to Islamabad’s profound insecurities stemming from conventional military disparities with India.

Pakistan’s concerns are not unfounded from its perspective; the K-4’s range covers the entirety of its territory from safe Indian Ocean standoff distances, complicating pre-emptive detection and interception. This shifts the deterrence dynamic, compelling Pakistan to invest further in submarine detection networks, anti-submarine warfare assets, and its own sea-based deterrents like the Babur-3 SLBM. Yet, experts view these reactions as exaggerated posturing to garner international sympathy and domestic support.

In stark contrast, China’s official reaction to the K-4 test has remained subdued, reflecting Beijing’s broader strategic priorities. Rear Admiral Shrikhande observes that China’s nuclear arsenal was originally driven by threats from the former Soviet Union—and persists amid tensions with Russia and the United States—rather than India. New Delhi simply does not rank as a primary peer competitor in China’s nuclear threat matrix.

That said, China employs subtle monitoring tactics, frequently deploying ocean research vessels equipped with hydrophone arrays and sonar buoys to shadow Indian submarine activities in the Indian Ocean. These “fishing” or “scientific” ships provide real-time intelligence on SSBN patrols, missile test trajectories, and underwater noise signatures. Such surveillance underscores Beijing’s quiet vigilance without overt provocation.

India’s sea-based deterrence fits into a broader triad maturation process. Complementing the Agni-series land-based missiles and air-delivered gravity bombs from Rafale and Mirage fighters, the underwater leg ensures survivability against surprise attacks. The anticipated S4 and S4* variants of the Arihant class, along with the larger S5 boats, will accommodate longer-range K-5 SLBMs (5,000+ km), further expanding bastion options.

Challenges persist, however. Building a credible SSBN fleet demands quiet propulsion systems to evade detection, a robust nuclear fuel cycle for extended patrols, and seamless command-and-control integration with the Strategic Forces Command. India’s indigenous efforts, led by the Defence Research and Development Organisation (DRDO) and Bharat Dynamics Limited, have overcome many hurdles, but scaling production remains key.

Geopolitically, this capability reassures partners like the Quad nations (US, Japan, Australia) of India’s role in countering Chinese maritime assertiveness. It also deters adventurism along the Line of Actual Control (LAC) or Line of Control (LoC), as adversaries must now factor in inescapable retaliation. The K-4 test thus recalibrates regional power balances, affirming India’s no-first-use policy with credible second-strike assurance.

Looking ahead, integration of emerging technologies—such as hypersonic glide vehicles on future SLBMs or AI-enhanced underwater drones—could elevate this deterrent further. As Rear Admiral Shrikhande asserts, India’s progress positions it for strategic stability, compelling neighbours to recalibrate rather than escalate. In an era of proliferating threats, a mature sea-based triad cements India’s status as a responsible nuclear power.

Based On Bharat Shakti Report