India Should Plan a Fleet of Six-SSBNs for Continuous at-sea Deterrence | The Financial Express

India Should Plan a Fleet of Six-SSBNs for Continuous at-sea Deterrence

This article tries to assess the kind of SSBN force level Indian Navy would need to operationalise a CASD posture in the future.

Nuclear submarine INS Chakra
Nuclear submarine INS Chakra (File/Indian Navy)

By Anubhav Shankar Goswami

India is situated in a difficult weapons of mass destruction (WMD) region. The fact that both of its nuclear-capable neighbours—China and Pakistan—are engaged in a secret and extensive nuclear cooperation framework adds to New Delhi’s difficulties.Therefore, to create a robust nuclear deterrent, India has also embarked on developing the sea-leg of its nuclear triad, which is believed to be the least vulnerable and most survivable deterrence platform. With the launch of the third ballistic submarine missile of the Arihant-class in January 2022, which is capable of carrying intermediate-range Submarine Launch Ballistic Missiles (SLBM); India’s SSBN programme is maturing into a credible second-strike capability. Gradual addition of longer range SLBMs in future will allow the Indian Navy to exploit larger patrol areas afforded by longer range missiles through Open Ocean patrolling and have a permanent presence in the deep sea. Called continuous at-sea deterrence (CASD) posture in military parlance, permanent presence of an SSBN in the open ocean adds credibility to the sea-leg of a country’s nuclear deterrence.

This article tries to assess the kind of SSBN force level Indian Navy would need to operationalise a CASD posture in the future.

Minimum of two‘boomers’must be put to sea at all times

For permanent open ocean patrolling to be credible, Indianeeds at least a global format of four SSBNs. A global format of four SSB N sallows uninterrupted deterrence patrol “with at least one boat on patrol, one preparing for patrol, one returning to port, and one in maintenance”. Anything below four, it would not be possible for the Indian Navy to guarantee the invulnerability of its SSBN fleet for a number of reasons. First, CASD posture with only three boats in the fleet would put severe stress on the Indian Navy as the “permanence at sea of an SSBN under good conditions of dilution (guaranteeing its invulnerability) would no longer be possible”. Second, the fourth boat also offers substitute cover in case of an ‘act of God’ occurrence, such as a mistaken collision with a friendly or hostile nuclear submarine.

Moreover, India is sandwiched between two belligerent powers with nuclear weapons. To credibly deter both China and Pakistan, India might need at least two SSBNs on continuous patrol, which is impossible to achieve with only three vessels in the fleet. In times to come, China’s Anti-Submarine Warfare (ASW) capabilities will greatly increase in effectiveness. People’s Liberation Army Navy (PLAN) has already intensified the regular visits of its SSNs to the Indian Ocean. Chinese ASW forces will naturally find it easier to identify or follow a solitary Indian SSBN on patrol. If the Indian Navy deploys multiple SSBNs on open ocean patrol, the risk that it may lose the ability to conduct a second-strike while at sea may be significantly reduced. The SSBN force is also less vulnerable overall if it has two or three boats at sea as opposed to one since a nuclear assault on their base is more likely to just result in the loss of one SSBN. In the foreseeable future, all of India’s nuclear-powered submarines, both SSBNs and SSNs, will be home stationed at the sole underground naval base, INS Varsha. Reportedly the base will be able to withstand even nuclear attacks. However, technological breakthroughs support offense more than defence and INS Varsha’s fortitude against future nuclear capabilities can never be fully assured. Therefore, it is strategically prudent for the Indian Navy to put at least two SSBNs permanently at sea. Finally, in the face of rapid modernization of its nuclear forces by China that will see its nuclear inventory skyrocket to 1000 warheads by 2030, having two or more SSBNs permanently at sea will enable New Delhi to continue upholding ‘credible minimum deterrence’ against Beijing.

‘S-5’ Class should be prioritised

Putting two SSBNs to sea for continuous at-sea deterrence, however, will require the Indian Navy more than a fleet of four ballistic missile submarines. During the cold war, France had a fleet of six Le Redoutables to maintain a CASD of two/three boats. A fleet of minimum six SSBNs is what New Delhi should also look at so that two vessels could be sent for continuous patrolling at all times, while retaining the option to slip a third boat during times of crisis.

With three more SSBNs to come, the Arihant class will have a strength of four in total. In the future, when the proposed S-5 class will join the Indian Navy, utility of the first-generation Arihant and Arighat will shrink due to their credibility issues. Currently operational Arihant and soon-to-be commissioned Arighat lacks the sufficient range in its SLBMs (K-15) to either target Islamabad or Beijing. However, the much bigger S-5 class, with twice the weight of the Arihantis expected to carry 12 K-6 SLBMs of intercontinental range of 6,000 km. It is unclear how many ‘boomers’ the Indian Navy is looking for the S-5 class. But since the Navy would most likely be interested in maintaining a CASD posture, a minimum of two S-5s will certainly be on the cards to fill the void left by Arihant and Arighat whenever they are decommissioned. It would do well for the Indian Navy to start thinking about having at least four boats of S-5 as well. Four S-5s, with the capability to strike all of China, would act as a formidable force multiplier to the third and the final boats of the Arihant class, the upgraded and upcoming S-4 and S-4*,which will carry eight intermediate range K-4 SLBMs. Therefore, it is imperative upon Indian defence establishment to expedite work on the S-5 class so that they can be commissioned sometime around the late 2030s.

Author is a Research Associate at Centre for Air Power Studies in New Delhi. Additionally, Anubhav is a Doctoral Scholar at Jindal School of International Affairs, O.P Jindal Global University. Email:; LinkedIn: Anubhav GoswamiTwitter: Anubhav Shankar (@Shankar5Anubhav)

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First published on: 18-01-2023 at 18:26 IST