Real impetus for India's expansion of its second-strike capability is, in fact, the significant growth of the Pakistani and Chinese navies in the Indian Ocean

by Abhijit Singh

India has just inducted its second indigenous nuclear ballistic missile submarine (SSBN), the INS Arighat. Unlike INS Arihant, India's first SSBN that served primarily as a technology demonstrator, the Arighat is a more advanced and operations-focused platform. It has reportedly benefitted from the extensive testing and validation of the Arihant’s systems, including its nuclear reactor, propulsion, and missile launch capabilities — all crucial aspects in developing SSBNs.

In core-capability terms, however, the INS Arihant and INS Arighat are quite similar. Both submarines weigh about 6,000 tonnes, are powered by an 83 MW pressurised water reactor, and are armed with K-15 nuclear ballistic missiles, which have a range of 750 km. Observers suggest that the anticipated expansion in deterrence capabilities will occur with the commissioning of the third SSBN, INS Aridhaman, expected next year. This slightly larger, 7,000-tonne vessel will be equipped with K-4 submarine-launched ballistic missiles (SLBMs) with a striking range of 3,500 km. The Aridhaman will be followed by another advanced SSBN, the codenamed S-4, and another unnamed fifth SSBN to be armed with the 5,000-km range K-5 submarine-launched ballistic missile.

Expectedly, Arighat’s commissioning has sparked speculation about a possible long-range patrol with nuclear ballistic missiles. It isn’t clear yet if there are any plans to test-fire the K-4 missile from the submarine, but this seems plausible, as the missile has only been tested from a submerged pontoon so far. A missile test from Arighat would significantly bolster India’s deterrence credibility. Even so, challenges remain. Targeting an SSBN in the deep ocean is difficult, as is maintaining effective communication with command authorities. Nuclear command and control on SSBNs is maintained through a system of controls involving de-mated missile systems and permissive action links — devices that prevent unauthorised arming and launching of nuclear weapons without the proper codes from the command authority. The problem for India’s strategic planners is that SSBNs communicate via very low-frequency systems, which limit the types of messages they can receive. It raises the possibility that the submarine could miss a code from the command authority to arm a missile and carry out a strike.

Even if it manages to overcome the communication challenge, it would take at least three SSBNs with long-range missiles to establish a credible sea-based deterrent. The 750-km range of the K-15 missile is insufficient to target key strategic areas in hostile countries. Observers say a truly credible deterrence posture isn’t achievable until the K-4 missile is deployed on the Aridhaman and the larger, more capable platforms are commissioned.

The delay in Arighat’s commissioning should give Indian analysts pause. Launched in 2017, the submarine has taken over six years to be inducted into service. Even considering the lengthy timelines required for SSBN trials — including the time needed to test machinery, sensors, and command and control and communication systems — the delay is substantial.

Why, some wonder, is India investing in expanding its nuclear ballistic missile submarine capability when it should be focusing on conventional and nuclear attack submarines? The concern seems valid until one considers that India needs both warfighting submarines and SSBNs. While attack submarines (SSNs) are designed for warfighting, SSBNs are essential deterrence assets, providing India with a reliable second-strike capability in the event of a nuclear first-strike by an adversary.

The real impetus for India's expansion of its second-strike capability is, in fact, the significant growth of the Pakistani and Chinese navies in the Indian Ocean. While Pakistan is set to acquire eight Chinese Type 039B Yuan-class submarines — with the first of the class launched in April this year — China's PLA Navy (PLAN) is focussing on two new classes of nuclear submarines: The Type 95 attack submarine and the Type 96 nuclear ballistic missile submarine. Worryingly, the power asymmetry between India and China remains stark — with the PLAN fast expanding its fleet to 60 submarines, including six SSBNs, six SSNs, and 48 diesel-electric submarines — while Pakistan continues to narrow the sea-power differential with India.

A related issue is India’s nuclear doctrine. As competition in the Indian Ocean intensifies, there is an ongoing debate about whether India should reconsider its No First Use (NFU) policy. Critics argue that the boundaries between conventional and nuclear deterrence are increasingly blurred and that the three core tenets of India’s nuclear doctrine — credible minimum deterrence, massive retaliation, and NFU — are no longer relevant. They assert that India’s commitment to NFU and "minimum deterrence" limits the size of its arsenal to a level insufficient for credible deterrence, especially as China and Pakistan continue to upgrade their arsenals.

India, however, is unlikely to alter its NFU and massive retaliation policy. Many within the country’s security establishment believe that modifying the nuclear doctrine could have adverse implications. Not only would abandoning NFU require substantial investments in financial and technological resources to make a 'first use' credible, but an aggressive nuclear stance could also trigger an arms race in the subcontinent and the wider Indo-Pacific region. The commissioning of INS Arighat has brought this delicate issue back into focus.

Abhijit Singh is the head, Maritime Policy Initiative at ORF New Delhi and a former naval officer. The views expressed are personal