India is actively advancing its submarine capabilities through a significant acquisition program known as Project 75 (India), or P75(I). This initiative is crucial for enhancing the Indian Navy's capabilities amid growing concerns over China's expanding submarine fleet in the Indian Ocean

Nuclear Deterrent

India’s second Arihant-class nuclear ballistic missile submarine (SSBN), INS Arighat, was commissioned into the Indian Navy on August 29. The new submarine brings India one step closer to a nuclear second-strike capability while also entrenching nuclear competition in the Indo-Pacific.

SSBNs are a potent and highly specialised military asset. Operated by only the United States, Russia, China, the United Kingdom, France and India, these boats are armed with submarine-launched nuclear ballistic missiles.

Due to their inherent stealth and ability to evade detection and survive a first strike, these submarines are designed to provide a reliable second-strike capability and underpin strategic nuclear deterrence via the principle of mutual assured destruction.

Like its predecessor INS Arihant, INS Arighat has four launch tubes, and can carry either 12 K-15 Sagarika submarine-launched ballistic missiles (750 kilometres range) or four K-4s (3,500 kilometres range). Submarine specifics are tightly held, and photos are hard to come by. India’s third SSBN, named INS Aridhaman, is scheduled to be commissioned in 2025, and a fourth is currently under construction.

India’s nuclear weapons program made various advances in 2024. In March, India successfully tested its Agni-V land-based intercontinental ballistic missile with multiple independently targetable re-entry vehicles – further closing the technological gap between India and China.

Despite commissioning its second SSBN, India’s submarines alone will not achieve the coveted “Continuous At Sea Deterrence” status – whereby at least one nuclear-armed submarine is on deterrence patrol at any one time, enabling a retaliatory strike and thereby deterring adversaries. A fleet of at absolute minimum three SSBNs is required to ensure one submarine is on deterrence patrol at any one time – the United Kingdom and France achieve continuous deterrence with four submarines each.

"Protecting the submarines comes at a high financial and opportunity cost, which may limit the Indian Navy’s ability to undertake less pressing, but nevertheless important missions."

India's Sub Hunt

India's ambitious submarine acquisition program is a crucial component of its maritime strategy, aimed at bolstering its naval capabilities and ensuring security in the Indian Ocean region. The increasing geopolitical significance of the region, coupled with the growing threat of submarine warfare, has necessitated India's focus on underwater dominance.

The project aims to construct six advanced diesel-electric submarines, featuring enhanced sensors, weapons, and air-independent propulsion (AIP) systems. The AIP technology allows submarines to remain submerged for extended periods, significantly improving their stealth and operational effectiveness.

The program mandates that the first submarine must incorporate at least 45% indigenous content, increasing to 60% for the sixth submarine. This aligns with India's broader goal of achieving self-reliance in defence manufacturing.

The first submarine is expected to be delivered seven years after the contract is signed, with subsequent units delivered at a rate of one per year.

The urgency of Project 75(I) is underscored by the increasing presence of Chinese submarines in the region. The Indian Navy is not only enhancing its conventional submarine fleet but also expanding its nuclear capabilities. Recently, India commissioned the S3 Arighat, its second nuclear-powered ballistic missile submarine, which bolsters its sea-based nuclear deterrence against potential threats, particularly from China.

Competitive Landscape

India's submarine acquisition is competitive, with various international shipbuilders vying for contracts. German firm Thyssenkrupp Marine Systems (TKMS) and Spanish company Navantia are both offering advanced submarine designs, emphasizing technology transfer and indigenization to meet India's defence needs. The Indian Navy is currently evaluating these proposals based on recent field trials of their respective AIP systems.

While India has made significant strides in its submarine program, it faces several challenges:

Some critical technologies, such as advanced propulsion systems and sensors, may still require foreign assistance. Delays in procurement and construction can hinder the timely development of submarine capabilities.

The substantial costs associated with submarine development and maintenance can pose budgetary challenges. Despite these challenges, India's submarine hunt presents significant opportunities:

The program can foster the development of indigenous defence industries and create jobs.

A strong submarine fleet can provide a strategic advantage in the Indian Ocean region and deter potential adversaries. India can leverage its submarine program to drive technological advancements in marine engineering and related fields.

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