From Foxtrot to Arighat: Evolution of India's submarine fleet

India's maritime boundaries, stretching over 7,500 kilometres, encompass vital regions of the Indian Ocean that are key to the country's maritime strategy. These waters have long required a robust naval presence to protect trade routes, natural resources, and national security interests.
At the heart of India's maritime strategy lies the Indian Navy's submarine fleet. What began as a modest force has transformed into a sophisticated arm capable of deterrence and power projection.

This transformation, from Soviet-supplied Foxtrot-class submarines in the 1960s to the impending realisation of an indigenous nuclear-powered attack submarine (SSN) fleet, reflects India's growing maritime ambitions and strategic foresight. Asianet traces India's submarine journey, highlighting the critical milestones that have shaped its development, culminating in the recent approval of homegrown SSNs— a landmark moment in the country's pursuit of maritime self-reliance and regional dominance.

The early years: From Foxtrot to Kalvari

India's submarine ambitions emerged in the tense geopolitical landscape of the 1960s. Following the 1962 Sino-Indian War and growing naval threats from Pakistan, India recognised the need for a credible underwater force. In 1965, India turned to its Cold War ally, the Soviet Union, establishing a long-standing partnership that would fundamentally shape its naval capabilities.

In December 1967, the Indian Navy commissioned its first submarine, INS Kalvari, a Soviet-built Foxtrot-class vessel. This marked a turning point for India's naval aspirations. Although the Foxtrot-class submarines were conventional, powered by diesel-electric engines, they provided India with crucial experience in underwater warfare.

Subsequent additions like INS Khanderi, INS Karanj, and INS Kursura built a modest but capable fleet focused on coastal defence, anti-surface warfare, and limited anti-submarine operations. Despite their limited range and the need for frequent surfacing, these early submarines laid the foundation for India's underwater capabilities, providing operational experience and setting the stage for future developments.

Indo-Soviet collaboration: The Foxtrot and Kilo classes

The acquisition of the Foxtrot-class submarines marked the beginning of a deep naval collaboration between India and the Soviet Union, which continued to evolve over the following decades. This partnership culminated in the induction of the Kilo-class submarines in the late 1980s, a significant upgrade over their predecessors.
Known in India as the Sindhughosh class, Kilo-class submarines offered significantly improved endurance, advanced sonar systems, and superior anti-ship missile capabilities. Their deeper diving capacities and quieter operations allowed extended patrols, providing a critical advantage in countering Pakistan's naval ambitions and monitoring China's expanding influence in the Indian Ocean.

While the Kilo-class was a crucial enhancement of India's conventional submarine fleet, the limitations of diesel-electric propulsion—most notably the need for frequent surfacing—highlighted the strategic need for nuclear-powered submarines. India was now poised for its next leap in submarine warfare.

The nuclear Age: The arrival of INS Chakra

India's desire for nuclear-powered submarines became a reality in 1987 when it leased the Charlie-class INS Chakra from the Soviet Union. This was a pivotal moment in Indian naval history. Unlike conventional submarines, nuclear-powered vessels could stay submerged for months, providing unmatched stealth, speed, and endurance. The induction of INS Chakra marked India's entry into an elite club of nations operating nuclear submarines, providing invaluable experience with nuclear propulsion systems and advanced underwater combat operations.

Although INS Chakra was returned to the Soviet Union in 1991, the experience gained during its operational period proved critical for India's indigenous nuclear submarine program. This initiative culminated in a second lease of an advanced nuclear submarine in 2011—the Akula-class INS Chakra II—which enhanced India's nuclear capabilities and prepared the Navy for its ultimate goal: building a fully homegrown SSN fleet.

Building indigenous capability: From HDW to Scorpene

India's reliance on foreign technology for its submarine fleet was never intended to be permanent. Early indigenisation efforts began in the 1980s with the HDW project, a collaboration with West Germany to build Shishumar-class submarines. Despite setbacks, the project laid the foundation for domestic submarine construction at Mazagon Dock Limited (MDL).

The next breakthrough came with Project 75, a collaboration with France's Naval Group to construct Scorpene-class submarines. These submarines introduced modern features such as advanced sonar, stealth operations, and state-of-the-art weapon systems. The commissioning of INS Kalvari in 2017 was a significant milestone, showcasing India's growing ability to produce sophisticated, stealthy submarines domestically.

The SSBN program: Strategic deterrence with Arihant-Class

In parallel with its conventional submarine advancements, India embarked on a strategic project to develop nuclear-powered ballistic missile submarines (SSBNs), bolstering the country's second-strike capability—a core component of its nuclear deterrence strategy. The Arihant-class SSBNs, designed to carry nuclear missiles, placed India among a select group of nations capable of operating these advanced vessels.

INS Arihant, commissioned in 2016, became India's first operational SSBN. It completed the nuclear triad alongside land-based missiles and air-delivered nuclear weapons. Its significance lies in its ability to ensure a credible retaliatory capability, thereby reinforcing India's nuclear deterrence posture.

INS Arighat: Strengthening the nuclear triad

Building on the success of INS Arihant, INS Arighat was inducted into the Strategic Forces Command in August 2024. As India's second SSBN, Arighat features enhancements that improve both survivability and strike capacity. Powered by an 83 MW pressurised light-water reactor and equipped with K-15 missiles (750 km range) and K-4 missiles (3,000+ km range), Arighat significantly enhances India's nuclear deterrence.

Its stealth capabilities, extended endurance, and precision strike ability add to India's strategic reach while showcasing advancements in indigenous submarine design and construction.

INS Aridhaman: The next leap forward

Set to join the Indian Navy by early 2025, INS Aridhaman represents the next evolution in India's SSBN program. Larger and more advanced than its predecessors, Aridhaman boasts a 7,000-tonne displacement and the ability to carry a greater payload of K-4 nuclear-tipped missiles. Future plans include upgrading its reactor to 190 MW, significantly enhancing its operational endurance and stealth capabilities.

The ability to remain submerged for longer periods, combined with its increased missile capacity, makes Aridhaman a formidable platform for strategic deterrence, further bolstering India's sea-based nuclear defence.

Enhancing the Indian Navy's strategic capabilities

The induction of INS Arighat and the upcoming INS Aridhaman significantly strengthen India's naval power in several key areas:

1.    Geopolitical Considerations: The growing presence of the Chinese People's Liberation Army Navy (PLAN) in the Indian Ocean has made it imperative for India to develop a stronger submarine fleet capable of projecting power and maintaining deterrence in the region.
2.    Strategic Deterrence: Both SSBNs form the backbone of India's sea-based nuclear deterrent, complementing land- and air-based missile systems. By ensuring credible second-strike capability, India can uphold its "No First Use" policy while deterring adversaries from launching a nuclear strike.
3.    Indigenisation and Self-Reliance: These submarines are part of the Advanced Technology Vessel (ATV) project, India's ambitious program to develop SSBNs and SSNs indigenously. The project strengthens India's defence manufacturing base and reduces reliance on foreign technology, which aligns with the Atmanirbhar Bharat initiative.

Global context and strategic balance

Though India's SSBN program is smaller in scale than the fleets of the US, China, or Russia, it plays a critical role in maintaining regional deterrence. China's Jin-class SSBNs, equipped with JL-3 missiles capable of striking targets up to 10,000 km away, present a strategic challenge to India. However, India's K-4 missiles, with a 3,000+ km range, offer credible deterrence within the Indian Ocean context. As India continues to develop more advanced SSBNs and SSNs, its ability to counter regional threats will grow, ensuring strategic parity amid rising tensions in the Indo-Pacific.

On the path to strategic deterrence

The commissioning of INS Arighat and the impending induction of INS Aridhaman mark pivotal moments in India's naval evolution. These submarines enhance India's strategic deterrence capabilities and highlight the country's growing self-reliance in defence technology. By strengthening the sea-based leg of its nuclear triad, India is positioning itself to secure its interests in an increasingly contested Indo-Pacific region.

As India looks to the future with plans for larger SSBNs and advanced SSNs, its submarine fleet will play a critical role in the nation's strategic defence, ensuring both deterrence and operational flexibility. The evolution of India's submarine force is a testament to technological advancement and a reflection of its broader ambitions to shape its destiny on the global stage.