Earlier this week, Indian Navy launched its fourth indigenously built nuclear-powered ballistic missile (SSBN) submarine at Ship Building Centre (SBC) in Visakhapatnam, to strengthen its nuclear deterrence against its adversaries. The low-key launch event comes amidst the de-escalation with China and a diplomatic spat with Canada. The newly launched SSBN is code-named S-4* and can launch nuclear-tipped missiles. The government has been close-lipped on nuclear deterrence, the fourth SSBN was launched a day after Defence Minister Rajnath Singh inaugurated the Very Low-Frequency Naval Station in the Damagundam forest area of Vikarabad district in Telangana. The Naval station is equipped for command, control and communications with strategic assets of the Indian Navy. This submarine is bigger and more capable than the first, INS Arihant (S2).
Earlier this year, the Indian Navy inducted its second SSBN, INS Arighaat on August 29, 2024. The third submarine INS Aridhaman (Destroyer of Enemy) is expected to be commissioned in 2025, while India's first Indigenous SSBN was launched in 2009 and quietly commissioned in 2016 by the Indian Navy. On October 9 this year, the Cabinet Committee on Security (CCS) cleared the Indian Navy's plans to construct two nuclear-powered attack submarines to dissuade any adversaries in the Indo-Pacific.
On October 22, Vice Chief of the Navy, Vice Admiral Krishna Swaminathan, said, "The SSBN programme is a successful one. Two submarines have been commissioned, and it is natural that others will follow," when reporters asked for his comment on the launch of the nuclear-powered submarine.
Second-Strike Capability Bolstered with the New S4
With nearly 75 % Indigenous content, the newly launched S4* SSBN has a 3,500 kilometers range of K-4 nuclear ballistic missiles, which can be fired through vertical launching systems. The first of its class INS Arihant carries 750 km range K-15 atomic missiles. Similarly, INS Arighaat is also armed with K-15 missiles with a range of 750 kilometers which limits their strike capabilities. Even in a conflict with Pakistan, these missiles would only have targets within its range in the south of the country. However, the successors are all upgraded to the previous ones and carry K-4 ballistic missiles.
SSBN has unlimited range and endurance, however, it is constrained only by food and supplies, crew fatigue and maintenance. Presently, both INS Arihant and INS Arighaat are on deep-sea patrols. And the new nuclear-powered attack submarine of the Russian Akula class is set to join the force in 2028.
Once INS Aridhaman (official name to be announced later), the fourth indigenously built submarine of this class is inducted into the Indian Navy, it will mean that India's second-strike nuclear capabilities will be fully operationalized by next year. INS Aridhaman is equipped with K-4 submarine-launched missiles and can travel 3500 km.
So far, India has two indigenously developed short-range submarine-launched ballistic missiles (SLBMs) including INS Arihant, and INS Arighaat. The third of this class of indigenously built nuclear submarine S4* gets its name from INS Chakra as S1 since national security planners named India's first leased nuclear attack submarine INS Chakra as S1, INS Arihant as S2, INS Arighaat S3, and hence the newly launched one is the last one of its class S4* with the formal name yet to be given.
The next class of Indian SSBNs will be double the 6,000-ton displacement of the Arihant class and will have nuclear missiles upward of the range of 5,000 kilometers and beyond. The focus on enhancing the nuclear power in sea by the government and the Indian Navy is based on the fact that aircraft carriers are vulnerable to long-range PLA missiles like Dong Feng-21 and Dong Feng-26 of one of India's powerful adversaries, China. It is also a reason that the priority has been given to nuclear attack and ballistic missile submarines over the third aircraft carrier for the Indian Navy. Additionally, the Indian Navy will also launch INS Vagsheer – a conventional submarine deterrence with the sixth of the diesel attack Kalvari class submarine – commissioned in December this year.
Meanwhile, the government has also collaborated with the French Naval Group to construct three more advanced diesel attack submarines at Mazgaon Dockyards. Since last year, the Indian Ocean has 10-11 warships every month and carrier-based long-range patrols are expected in 2025-26, these strategic submarines will play a major role in defending India and dominating the Indian Ocean Region (IOR).
Why continuous patrol is key to India's Nuclear Deterrence
The level of survivability amidst nuclear conflict lies in equipping nuclear-powered ballistic missiles with enough ranges. So far, the submarine-launched ballistic missile has been considered the most survivable delivery system in the opaque ocean depths. Thus, induction of S4* will significantly boost India's nuclear deterrence. The absence of at least three active submarines means that the submarines are mostly in and out of the harbour impacting constant atomic deterrence in sea.
A nuclear-powered attack submarine or SSBN ensures the survivability of nuclear retaliatory capability. "The SSBN can remain hidden in ocean depths during the conflict and ensure the survival of second-strike capability with its long coastlines and peninsula," a senior naval officer told ETV Bharat. To explain it further, the Indian Navy needs continuous nuclear deterrence and for that one submarine always needs to be on patrol. "For instance, if Arihant is in and out of the harbour, it is not a deterrent as it is out and not in the depth of the sea. Thus, at least 3-4 SSBNs are needed – one to be on patrol when one is in port, one to go for patrol, and one comes back – to ensure that there is constant deterrence at sea," he said.
India's new class of SSBNs (S-4 and S-4*) draw construction expertise from INS Arihant and INS Aridhaman – both advanced technology vessels.
In 2021, satellite imagery of S-4 surfaced which confirmed that at 7,000 tonnes, S4 SSBN was slightly larger with a load of water line measurement of 125.4m compared with 111.6m of the 6,000-tonne INS Arihant, the first boat of this class.
Considerably, SSBNs strengthen nuclear deterrence. Take the British Royal Navy, the UK's Sea deterrence, which is one of the longest-sustaining military operations with its 53rd year of maintaining sea legs of nuclear deterrence.
A Strategic Shift - Nuclear Submarines Over Aircraft Carriers
Presently, only China has SSBNs in the Indian neighborhood, which have been deployed for "counter-piracy patrols" off the east coast of Africa. However, Chinese anti-submarine warfare is at an initial stage. There have also been reports that the Pakistan Navy is exploring to equip its under-construction Chinese Hangor-class submarines with nuclear-powered missiles to explore its sea-based deterrence. A retired Pakistan naval officer did talk about Islamabad working towards an "assured" second-strike capability on the state-owned television network. There have also been reports about China's acquisition of Hangor-class submarines. Vice Admiral Ahmed Saeed of Pakistan Navy did indicate that the submarine would be a "hybrid" piece in Pakistan's broader deterrence posture.
These developments murky the Indian Navy's undersea waters. Hence, it is strategically important for the Indian Navy to build its submarine capabilities. In October 2024, the Indian government authorized the construction of the country's first nuclear-powered attack submarine (SSN).
Given the growing power of the Chinese Navy, it is critical for the Indian Navy to match the former's sea strength with nuclear-powered submarines. The Indian Navy has reportedly put on hold its projects to build a 65,000-ton Indigenous Aircraft Carrier (IAC)-2 to advance the SSN project.
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