On November 4, 2018, Indian prime minister Narendra Modi announced that  the Arihant, the Indian Navy’s first domestically-built nuclear-powered  submarine, completed her first deterrence patrol. The Arihant, which  means “Slayer of Enemies” in Sanskrit, uses a uranium-fueled pressurized  light-water reactor to generate 83-megawatts of electricity, allowing  the submarine to swim underwater for months at a time at speeds as high  as twenty-four knots.
Even more important than the Arihant’s  propulsion system, however, are the weapons presumably stowed in her  four vertical launch tubes: up to a dozen K-15 Sagarika (“Oceanic”)  nuclear-tipped missiles designed to launch from underwater to annihilate  an adversary’s cities and military bases. (Note that the warheads are  usually stowed separately from the missiles per Indian doctrine.)
The  Arihant is the lead-ship of India’s most expensive defense program  ever, valued at $13 billion, with its origins in the secretive Advanced  Tactical Vessel program in the 1990s. Indian engineers received  substantial Russian assistance designing the Arihant, basing her in part  on the Russian Akula-class attack submarine, one of the quietest types  operated by the Russian Navy. The Indian Navy’s only other operational  nuclear-submarine is the Akula-class Chakra II under lease from Russia  through 2022.
However, instead of developing an attack sub for  hunting enemy warships and submarines, India’s Defense Research and  Development Organization (DRDO) wanted a nuclear-powered ballistic  missile submarine (SSBN or “boomer”) to complement India’s land- and  air-based nuclear forces . Because nuclear-powered submarines can remain  submerged for months at a time and deliver their weapons from  underwater, they are considered the asset most likely to survive a  nuclear “first strike” by an adversary, guaranteeing an apocalyptic  second strike in retaliation.
The Arihant was launched in 2009  but underwent seven years of testing and sea trials before finally being  discreetly commissioned in August 2016. However, just four months  later, a hatch left open in port caused the 6,500-ton submarine to flood  with corrosive saltwater. Because of the bizarre mistake, the Indian  Navy was forced to delay deployment for 10 months to replace the  submarine’s pipes.
Even with completion of Arihant’s first  patrol, however, India’s sea-based nuclear deterrence will require years  more of work before it becomes fully credible.
To start with,  the Arihant’s ten-meter long K-15 missiles have a range of only around  430 miles, meaning that they cannot strike inland Pakistani targets,  including the capital Islamabad. Nor could K-15s hit Chinese cities when  launched from the Indian Ocean.
The DRDO has developed a  twelve-meter tall K-4 Shaurya SLBM with a range of 2,100 miles that is  due to enter service in the early 2020s. Though the Arihant successfully  test-fired a K-4 in 2016 , technical problems reportedly scrubbed a  later test in 2017.
Once the K-4 enters service, the Arihant will  finally be able to serve as deterrence against both Pakistan and China.  However, the Arihant, which remains in many respects a testbed, can  only carry four K-4s—a fraction of the payload carried by most SSBNs  around the world.
The Indian Navy will also need more than one  SSBN so that at least a few can rotate on patrols, while others undergo  repairs or are used for training. Redundancy is also necessary so that  the loss of a single boat—whether to enemy action, accidents at sea, or  absent-minded maintenance—doesn’t cripple India’s sea-based deterrence.
Towards  this end, India has already launched a second Arihant-class submarine,  the Arighat, which is expected to be commissioned between 2019-2021. The  Arighat has a more powerful reactor and can carry twice the payload:  twenty-four K-15 missiles or eight K-4s. 
Additionally, the  Indian Navy has already begun construction of two to four more  Arihant-class boats of progressively larger configurations—dubbed the S4  and S4*—and carry 3,000-mile-range K-5 missiles. By the mid-2020s, the  DRDO then plans to begin construction of four larger and more advanced  S5 ballistic missile submarines which displace 15,000 tons and are armed  with twelve-sixteen launch tubes that can fire K-6 ballistic missiles.  These will have a range of 3,700 miles and separate into multiple  independent nuclear warheads (MIRVs) when reentering the atmosphere.
The  DRDO also intends to apply experience developing the Arihant towards  building six Chakra-III nuclear-powered attack submarines. Reportedly,  New Delhi’s decision to pursue the 60,000 crore ($8.4 billion) program  was prompted by the 2013 patrol of a Chinese Shang-class nuclear  submarine in the Indian Ocean. With a speed of thirty knots and  indefinite underwater endurance, the Shang-class could potentially hunt  down the slower Arihant-class, which has torpedoes for self-defense but  is not optimized for such a fight.
However, devising more  powerful nuclear reactors remains a stumbling block impeding development  of both the S5 SSBN and Chakra III. The former reportedly may require a  190-MW reactor.
By 2022, the Indian Navy will complete a nuclear  submarine base called INS Varsha, located on the central-eastern coast  of India, southwest of the shipyard at Visakhapatnam. Theoretically,  India’s boomers will depart from there on long, quiet patrols within the  “bastion” of the eastern Indian Ocean, with friendly air and naval  forces close at hand to ward away hostile sub-hunters. The submerged  subs would only launch their doomsday weapons upon receiving orders  transmitted via extremely-high-frequency radio from a national command  authority.
Despite the many milestones ahead for India to bring  its SSBN force to maturity, the Indian Navy may possess the missiles and  boats to maintain credible submarine nuclear-deterrence by the  mid-2020s.
Does this make the world a more dangerous place?  India, China and Pakistan between them have a population of 2.92 billion  people—nearly 39 percent of all human beings on the planet. A nuclear  conflict could easily claim tens, or hundreds of millions of lives.
Fortunately,  despite long-running tensions over their Himalayan borders, New Delhi  and Beijing both maintain a No-First-Use policy. This means their  militaries are authorized only employ their nuclear arsenals in  retaliation for an adversary’s nuclear strike. If both states stick to  that policy, neither will deploy nuclear weapons against the other.
Of  course, adherence to principle is hardly guaranteed in an anarchic  international system, particularly if a country believes it is facing an  existential threat. Nonetheless, the No-First-Use doctrine profoundly  impacts how India and China’s nuclear forces are equipped, trained and  organized—as well as how their respective governments signal to each  other internationally.
Pakistan, which is allied with China, is a  destabilizing factor: it has dispersed dozens of lower-yield tactical  nuclear weapons to its forward military units, and claims it is willing  to employ them in response to a non-nuclear attack. Unfortunately,  simulations suggested that tactical nuclear attacks on battlefield  targets are likely to initiate a tit-for-tat exchanges escalating to  horrifying strategic attacks targeting enemy populations. Pakistan is  also developing a submarine-based nuclear deterrent using simpler diesel  electric submarine that can launch nuclear-tipped Babar cruise missiles  .
As China is also developing a nuclear-capable stealth bomber ,  the world’s two most populous nations will soon likely boast full  nuclear deterrence triads on air, sea, and land. Hopefully, the  destructiveness of those capabilities will serve to make resorting to  nuclear arms an even more unattractive option for resolving disputes,  because the outcome of a regional nuclear exchange is horrifying to  contemplate.
 nationalinterest