The K-4, developed by India’s Defence Research and Development Organisation (DRDO) with a range capability of 3,500 km, will be an intermediate range submarine launched ballistic missile (SLBM).

The K-4 arms India’s first indigenously-built ballistic missile the Arihant class submarines, completing India’s nuclear triad of delivery vehicles.

The K-4 aboard the INS Arihant and future Indian SSBN’s will give India the ability to target most of China, including Beijing, and all of Pakistan when operating in the northern parts of the Bay of Bengal.

While technical details are hard to ascertain given the levels of secrecy involved, the K-4, which underwent its last test in March 2016, reportedly has a length of 12 metres, a diameter of 0.8 metres, and can carry a payload of up to 2 tonnes.

The missile is powered by solid rocket propellants and is highly accurate with a near-zero circular error probability according to the DRDO.

The INS Arihant will have the capability to carry four K-4 missiles, and the follow-on SSBN’s (Ship Submersible Ballistic Nuclear) that are planned will have the capacity to carry eight K-4 or such SLBM’s each. Future submarines will reportedly be larger and will carry missiles of longer range like the S-5, which will have a reach of over 5,000 kilometres.

New Delhi has an officially adopted posture of no first use and assured retaliation.

Hence, India considered it essential to develop capabilities to eventually deploy continuous at-sea nuclear deterrence to ensure the survivability of its nuclear second-strike capability.

In theory, a sea-based nuclear deterrent is invulnerable once undersea because it can hide and is not trackable or targetable by adversaries, unlike ground-based systems. This is especially important to India, as its land-based systems will have little reaction time given the proximity of Pakistani and Chinese nuclear weapons.

Pakistan Purchasing Yuan-Class Diesel-Electric Submarines

Pakistan has over the last few years pursued strategic parity with India’s growing underwater nuclear capabilities in an attempt to negate its conventional superiority.

The Pakistani navy created a strategic command a few years ago which went on to recently test a nuclear capable submarine launched cruise missile with a range of 450 kilometres in the form of the Babur III.

Islamabad has claimed second-strike capability. Pakistan is currently in the process of purchasing eight Yuan-class diesel-electric submarines from Beijing. Added to the existing three French Agosta-90B/Khalid and two Agosta-70 submarines of the Pakistan Navy and the ambiguity of deploying nuclear-armed cruise missiles on conventional submarines will be highly destabilising.

This would make prosecution of targets vis-à-vis Pakistan extremely difficult for the Indian Navy in the years to come.

China’s Nukes Can Destroy Most of India

China, on the other hand, has an operationalised at-sea nuclear deterrent and had sent a Jin-class SSBN out on its first deterrent patrol, according to press reports, in December 2015.

The submarine is armed with up to 12 JL-2 nuclear armed SLNM’s with a estimated range of 7,200 kilometres, meaning most of India falls within its range from its operating bastion of the South China Sea.

India’s eventual induction of SSBN’s in numbers armed with K-4 missiles is unlikely to change or draw any reaction from Beijing apart from an increase of probes by the Chinese Navy in the Bay of Bengal region to track and monitor patterns in India’s SSBN deployments.

From Civilian Control of Weapons To Military Control

Historically, Indian nuclear warheads and delivery systems are unmated and housed at different locations.

In a stark contrast and a first, deployment of an undersea launch capability will require weaponisation of the K-4 and represents a shift from civilian control of weapons to military control.

The induction in the future of the K-4 will require a review and strengthening of India’s C4ISR (Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance) capabilities and procedures to prevent any unauthorised commands or accidental launches.