IN the last week of 2025, India, as part of its ongoing naval modernization efforts, conducted a test launch of its K-4 intermediate-range submarine-launched ballistic missile in the Bay of Bengal off the coast of Visakhapatnam, with a reported operational range of approximately 3,500 kilometers.
The missile was fired from an underwater platform, specifically the nuclear-powered ballistic missile submarine INS Arighat, India’s first nuclear-powered ballistic missile submarine (SSBN). Also, India is reportedly developing the K-5 SLBM with an estimated range of over 5,000-8000 kilometers. Once operational, theK-5 will substantially enhance India’s sea-based nuclear capabilities, enabling it to reach distant targets across the entire Eurasian and African landmasses. India’s growing naval build-up is driven by its ambitions to establish a blue-water navy through a significant naval presence in the Indian Ocean and beyond, thereby making the sea a new threat domain and potentially sparking a conventional and nuclear arms race in the region.
Sea-leg capabilities, particularly nuclear-powered submarines, are considered the most survivable leg of the nuclear triad, providing credible deterrence against a nuclear rival. Over the decades, persistent improvements have made submarines one of the most potent and sought-after tools in maritime warfare, thanks to their unparalleled stealth, endurance and versatility. Theoretically, submarines provide a significant strategic advantage as they can operate undetected underwater for extended periods and conduct surveillance deep into enemy territory. On the other hand, conventional submarines remain relevant and are the key component of the naval capabilities of many countries across the globe. The conventional submarine has improved over time in Air-Independent Propulsion (AIP)—a technology that enables a diesel-electric submarine to operate underwater for extended periods without surfacing. The conventional submarine suits most countries well because they do not employ the submarine for distant offensive operations that require speed and long endurance. Second, conventional submarines are cheaper to buy. Nations with submarines near their borders focus on coastal and trade-route defense close to their home shores, and therefore, cheaper conventional submarines enhanced with AIP technology suit them well.
India`s continued modernization efforts and its nuclearization of the Indian Ocean further complicate deterrence dynamics by offering incentives to pre-emptive strategies and questioning India`s `No First Use’ policy, which is already in doubt. Though India’s official maritime security strategy and nuclear doctrine align with the traditional understanding that sea-based nuclear capability ensures a survivable second-strike capability, this may increase India’s temptation to adopt a counterforce-first-strike posture, thereby intensifying Pakistan’s threat perception. India’s development of sea-based nuclear capabilities, paired with longer-range delivery systems, has introduced a new risk of maritime crisis instability. India’s growing sea-based capabilities appear to be motivated by its long-standing efforts to enter the group of selected countries considered great powers, including the United States, Russia, China, France, and Britain, which possess such capabilities.
India`s naval modernization also aims to contain China, with control of the Indian Ocean being a particular area of contention and gain a strategic advantage over Pakistan through its sea-based capabilities. India’s nuclear weapons loaded in submarines would obviously be mated, providing more readiness for their use. Thus, this would be a noticeable departure from India’s existing policy, as previously delivery systems and warheads were stored separately. This could also increase the chances of miscalculations and inadvertent use, thus making the South Asian nuclear theatre even more unstable. The poor safety culture in India also raises doubts about the requirements for safe operations of such a complex technology.
As India modernizes its sea-based capabilities and deploys nuclear weapons on submarines, Pakistan is forced to take strategic countermeasures. Pakistan already possessed a modest second-strike capability. The Hangor-class submarine is expected to substantially enhance Pakistan’s Navy’s underwater capabilities and strengthen Pakistan`s sea-based deterrence. While these submarines are conventionally powered, they have compatibility with Pakistan`s nuclear-capable submarine-launched cruise missile Babur-3, thereby denying India the incentive for a preemptive counterforce strike and strengthening sea-based deterrence against India. Recently, the Pakistan Navy conducted a “comprehensive exercise” in the north Arabian Sea, successfully firing a surface-to-air missile and demonstrating both conventional and unmanned capabilities aligned with the evolving naval warfare.
During the military crisis in South Asia in February 2019, an Indian nuclear submarine was reportedly deployed. Similarly, in May 2025 conflict with Pakistan, India mobilized INS Vikrant. This indicates that the arms race in South Asia could move into sea-based deterrence and create a new theatre of conflict. The previous year witnessed key developments in the region, highlighting the growing risks of conflicts between the nuclear rivals and indicating perilous developments with serious risks of escalation in the region. Lastly, India`s expanding sea-based capabilities and the presence of external actors in the Indian Ocean mean that the maritime domain could become the primary domain in future conflicts.
—The writer is Associate Director Research, BTTN, at BUITEMS, Quetta.
