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Continuous at-sea deterrence

The third indigenous nuclear-powered ballistic missile submarine in the Arihant class is thought to weigh 7,000 metric tonnes and is assigned to the Strategic Forces Command

4 min read
Updated On: May 10 2026 | 5:16 PM IST
Satarupa Bhattacharjya
Indian Navy's INS Aridhaman, third indigenously built nuclear-powered ballistic missile submarine

Indian Navy’s INS Aridhaman, third indigenously built nuclear-powered ballistic missile submarine. Photo: PTI

India quietly inducted into service the INS Aridaman in early April. The third indigenous nuclear-powered ballistic missile submarine in the Arihant class is thought to weigh 7,000 metric tonnes and is assigned to the Strategic Forces Command (under the civilian leadership). India follows a policy of “minimum credible deterrence” and “no first use” of nuclear weapons. 
The Indian Navy, which is in charge of the submarine’s operations, didn’t issue a media statement, nor did the Ministry of Defence. On the day of the induction, only Defence Minister Rajnath Singh wrote on X that the word, Aridaman, which in Sanskrit means “vanquisher” or “destroyer” of foes, symbolises “power”. 
The strategic strike (S4) submarine, built in the city of Visakhapatnam, has a more advanced light water reactor than the INS Arihant (commissioned in 2016) and INS Arighaat (2024). The last known submarine-launched ballistic missile test for this class was carried out by the Arighaat in December. A missile series (the ranges have increased over time) for the submarines in India is K, named after the former president and rocket scientist A P J Abdul Kalam. This class of submarines is part of the advanced technology vessel programme, launched in the 1980s.
India has some 19 submarines, both conventional diesel-electric and nuclear-powered. A fourth SSBN (submersible ship ballistic missile nuclear) is being domestically developed. The addition of Aridaman raises India’s naval profile, veterans say.
“It’s a good thing — the third vector of the nuclear triad after the first two boats,” Admiral Karambir Singh (retired), former chief of the Indian Navy, said, adding that it enables India’s continuous at-sea deterrence (CASD). 

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The CASD is a naval doctrine of keeping at least one SSBN on patrol at sea, undetected and fully loaded, all the time. The practice is followed by some other nuclear-armed countries.
Building such a submarine is a complex process, which involves not just the reactor but also stealth features. 
Even a minor design flaw can be catastrophic for submarines (in general) which is why they take years to be completed.  
What India needs now are dozens of SSNs, according to an internal estimate.
An SSN (submersible ship nuclear) is a nuclear-powered attack submarine designed for stealth, speed and 
long-endurance operations. Unlike SSBNs, SSNs are deployed to track adversary submarines or ships. They carry torpedoes and cruise missiles. For instance, the United States (US) Navy vessel that destroyed an Iranian frigate near Sri Lanka during the recent West Asia conflict is an SSN.
India aims to build six SSNs under the Project 77 programme, with full commissioning of the vessels expected by 2036-37. 
“Nuclear-powered attack submarines are essentially needed, considering the opacity of the underwater domain in naval operations,” Singh said.   
India had signed a $3 billion contract to lease an SSN from Russia. The Akula-class nuclear-powered attack submarine (Chakra in India) will reportedly be handed over within two years. 
But building conventional submarines has been tougher for India. 
The indigenous design capability for a conventional submarine seems to be stuck, owing to the lack of critical technology, a government source said on the condition of anonymity. 
Designing the air-independent propulsion (AIP) system — essential to keep such vessels submerged for long and maintain low acoustic levels — is a technology that few countries have. Shipyards in India have yet to master it. 
India is looking to get six advanced conventional diesel-electric submarines, equipped with AIP, under the Project 75(I) programme. The state-run Mazagon Dock Shipbuilders Ltd will construct them in collaboration with Germany’s ThyssenKrupp Marine Systems.  
The Indian Navy needs more submarines and warships to reduce the number gap with China. India has more than 130 warships and submarines, less than half of China’s 250. China is estimated to have 60-70 submarines. The Indian Navy will induct more than 50 ships that are under construction, pushing the number to 180 by 2035. But some old ships will be decommissioned, possibly even the Arihant (eventually). Plus, the missiles on it have shorter ranges compared to the newer submarines in the same class.  
India commissioned some 30 major naval ships in the past decade, including aircraft carriers, conventional and nuclear submarines, destroyers, frigates, corvettes and survey vessels. China has three aircraft carriers, India has two. China is building a fourth carrier.  
India will need at least three carrier battle groups in the future, Indian Navy chief Admiral Dinesh Tripathi said at a news conference last year.
India’s defence shipbuilding has been slow for many reasons, including the lack of yards and bureaucratic delays. 
Like in the Speed Act of the US, some actions can be processed parallelly to cut acquisition timelines, Singh said. 
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Written By :

Satarupa Bhattacharjya

Satarupa Bhattacharjya is a journalist with 25 years of work experience in India, China and Sri Lanka. She covered politics, government and policy in the past. Now, she writes on defence and geopolitics.
First Published: May 10 2026 | 5:16 PM IST

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