Should India Convert Arihant-Class SSBNs into SSGNs? A Strategic Case for Redefining Undersea Power

What if India’s most secret and strategic naval assets are not the final form of its undersea power, but merely a transitional phase in a much larger transformation that has yet to fully unfold? What if the true strength of India’s submarine force does not lie only in its ability to deter nuclear conflict, but in its potential to redefine how power is projected beneath the oceans? As India steadily advances toward the next phase of its maritime evolution with the S-5 class of nuclear-powered ballistic missile submarines, a deeper and more consequential question emerges—one that goes beyond platform development and enters the realm of strategic doctrine itself. What should be done with the Arihant-class submarines once the responsibility of nuclear deterrence begins to shift toward more capable, longer-range platforms? The answer may not lie in redundancy or retirement, but in transformation, adaptation, and strategic foresight.

India’s nuclear doctrine has long been built upon the principle of credible minimum deterrence, a framework that emphasizes survivability, restraint, and assured retaliation rather than aggressive posturing. Within this doctrine, the nuclear triad—comprising land-based missiles, air-delivered weapons, and sea-based deterrence—forms the backbone of India’s strategic posture. Among these, sea-based deterrence is widely regarded as the most survivable component, as submarines operating in the vastness of the ocean remain the hardest to detect and neutralize. The induction of INS Arihant marked a historic milestone in India’s strategic journey, signaling its entry into an exclusive group of nations capable of deploying nuclear weapons from underwater platforms. This capability was further strengthened with the addition of INS Arighat and the development of follow-on vessels such as S-4 and S-4*, collectively forming the foundation of India’s sea-based nuclear deterrent.

However, while the Arihant-class represents a significant technological and strategic achievement, it operates within certain structural and operational constraints that become increasingly evident when viewed against the evolving geopolitical landscape of the Indo-Pacific. The submarines are currently equipped with submarine-launched ballistic missiles such as the K-15 and K-4, which, while effective within their operational parameters, impose limitations in terms of range and payload when compared to the capabilities being developed by other major powers. In practical terms, this means that for these submarines to effectively hold key adversarial targets at risk—particularly those located deep within the mainland of potential adversaries—they may need to operate closer to contested or heavily monitored maritime zones. In an era where anti-submarine warfare technologies are advancing rapidly, including the deployment of underwater sensor networks, maritime patrol aircraft, and unmanned systems, such proximity increases the risk profile of these platforms.

This is where the emergence of the S-5 program begins to fundamentally alter the strategic equation. The S-5 class, envisioned as a new generation of larger and more capable nuclear-powered ballistic missile submarines, is expected to displace approximately 13,000 tons and carry longer-range submarine-launched ballistic missiles such as the K-5 and K-6. These advancements would allow India to maintain a credible second-strike capability from safer distances, reducing the need for its submarines to operate in high-risk environments. In essence, the S-5 class represents not just an incremental improvement, but a qualitative leap in India’s deterrence posture. As these submarines become operational in the coming years, it is reasonable to assume that they will gradually take over the primary role of nuclear deterrence patrols, thereby redefining the operational relevance of the existing Arihant-class fleet.

It is at this juncture that a critical strategic opportunity emerges. Rather than viewing the Arihant-class submarines as assets that will eventually be overshadowed by more advanced platforms, India can choose to reimagine their role within a broader and more dynamic naval doctrine. One of the most compelling options in this regard is the conversion of these submarines from SSBNs—platforms designed primarily for nuclear deterrence—into SSGNs, or guided missile submarines capable of delivering conventional precision strikes. This concept is not without precedent. In the early 21st century, the United States Navy undertook a similar transformation by converting four of its Ohio-class submarine SSBNs into SSGNs. These converted submarines were equipped to carry a large number of Tomahawk cruise missiles and were capable of conducting a wide range of missions, including land-attack operations and special forces deployment. This transformation effectively turned platforms designed for nuclear deterrence into versatile instruments of conventional power projection.

For India, the strategic logic behind such a conversion is multifaceted. First, it addresses the issue of redundancy. As the S-5 class assumes the primary role of nuclear deterrence, the Arihant-class submarines may no longer be required to perform continuous deterrent patrols. However, this does not diminish their value; rather, it opens up the possibility of repurposing them for roles that are increasingly relevant in contemporary warfare. Second, it helps bridge a critical gap in India’s conventional strike capabilities. While India possesses a range of land-based and air-launched missile systems, its ability to conduct sustained and stealthy conventional strikes from underwater platforms remains limited. Converting Arihant-class submarines into SSGNs would enable the deployment of cruise missiles such as BrahMos or future long-range systems, allowing India to strike strategic targets with precision from concealed positions at sea.

This capability becomes particularly significant when viewed in the context of the Indo-Pacific region, where maritime competition is intensifying and the ability to project power across vast distances is becoming increasingly important. Against a backdrop of expanding naval capabilities and strategic presence by China, India must not only ensure the survivability of its deterrent forces but also develop the capacity to impose costs and shape outcomes in conventional conflict scenarios. SSGNs provide a unique combination of stealth, endurance, and firepower, enabling them to operate undetected while holding a wide range of targets at risk. In strategic terms, they introduce a layer of uncertainty that complicates adversary planning and enhances deterrence at multiple levels.

At the same time, the concept of conversion need not be viewed in isolation. A more comprehensive and forward-looking approach would involve not only the conversion of existing Arihant-class submarines but also the construction of additional submarines based on the same design lineage, purpose-built as SSGNs from the outset. This dual-track strategy would allow India to create a dedicated fleet of guided missile submarines optimized for conventional strike missions, rather than relying solely on retrofitted platforms. By leveraging the existing technological base and industrial ecosystem developed for the Arihant program, India can accelerate the development of such platforms while incorporating design improvements tailored to the specific requirements of SSGN operations, including increased missile capacity, enhanced stealth features, and greater mission flexibility.

Over time, this approach could lead to the emergence of a layered undersea force structure, comprising S-5 class SSBNs for nuclear deterrence, converted Arihant-class submarines serving as interim SSGNs, and newly constructed SSGNs forming the backbone of India’s conventional underwater strike capability. Such a structure would provide India with a balanced and versatile maritime force capable of addressing a wide spectrum of strategic challenges, from deterrence and defense to power projection and crisis response. It would also align with the broader trajectory of naval warfare, which is increasingly characterized by the integration of multiple domains and the need for platforms that can operate effectively across different mission profiles.

However, the path toward such a transformation is not without its challenges. From a technical perspective, converting SSBNs into SSGNs requires significant modifications to the submarine’s internal architecture, particularly the missile compartment. Ballistic missile tubes must be adapted or replaced to accommodate multiple cruise missiles, potentially through the installation of vertical launch systems. This involves complex engineering work, including structural reinforcement, systems integration, and extensive testing to ensure reliability and safety. Additionally, fire control systems, targeting mechanisms, and command-and-control frameworks must be reconfigured to support conventional strike missions, which differ fundamentally from the requirements of nuclear deterrence.

There are also doctrinal and strategic considerations to take into account. India’s nuclear posture has traditionally emphasized restraint and defensive deterrence, and any visible shift toward enhancing conventional strike capabilities must be carefully calibrated to avoid misinterpretation. The conversion of SSBNs into SSGNs could be perceived by some as a move toward a more assertive or offensive posture, particularly if not accompanied by clear communication of intent. It is therefore essential that such developments are framed within the context of strengthening conventional deterrence and maintaining strategic stability, rather than signaling a departure from established principles.

Industrial capability represents another critical factor. While India has made significant progress in building nuclear-powered submarines, large-scale conversion projects of this nature require a high degree of precision, expertise, and coordination across multiple domains. Shipyards, research institutions, and defense organizations must work in tandem to execute such a program successfully. This may necessitate further investment in infrastructure, workforce development, and technological innovation, as well as the establishment of robust project management frameworks to ensure timely and efficient execution.

Despite these challenges, the potential benefits of pursuing a combined strategy of conversion and new construction are substantial. In an era where the boundaries between deterrence and warfighting are becoming increasingly blurred, the ability to operate across both domains with flexibility and precision is a critical advantage. SSGNs embody this capability, offering a platform that can remain hidden, endure for extended periods, and deliver decisive effects when required. For a country like India, situated at the crossroads of major maritime trade routes and facing a complex and evolving security environment, such capabilities are not merely desirable—they are essential.

As the S-5 era approaches, India finds itself at a strategic inflection point. The decisions made in the coming years regarding the future of the Arihant-class submarines will have long-term implications for the country’s maritime posture and its ability to navigate the challenges of the Indo-Pacific. By choosing to convert existing platforms and invest in new SSGN construction, India can move beyond a singular focus on nuclear deterrence and embrace a more holistic approach to undersea warfare—one that integrates deterrence, dominance, and flexibility into a coherent strategic framework.

In the final analysis, the question is not simply whether India should convert its Arihant-class submarines into SSGNs. The deeper question is whether India is prepared to rethink the role of its underwater forces in a changing strategic landscape. The Arihant-class was born out of the need to establish a credible and survivable nuclear deterrent. That mission has largely been accomplished. The next phase requires a different kind of thinking—one that recognizes the value of adaptability, the importance of multi-role platforms, and the strategic advantages of operating in the gray zone between peace and conflict.

The silent depths of the ocean have always been a domain of uncertainty, where visibility is limited and outcomes are shaped by those who can operate with precision and foresight. In such an environment, the true measure of power lies not just in what a nation possesses, but in how it chooses to use it. By transforming its existing assets and investing in new capabilities, India has the opportunity to redefine its undersea strategy and position itself as a formidable maritime power in the decades to come.

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