ndia has secretly test fired its most potent submarine-launched ballistic missile (SLBM), which gives it the capability to nuclear-bombard a target on land 3,000 km away from an undersea firing platform. The successful maiden launch of the K-4 on 24 March marks one of the most significant advances in its nuclear weapons programme, say sources. This came ahead of the 16th anniversary of the 11 May 1998 Pokhran-II detonations, when India declared itself a nuclear weapons state.

"The K-4 is a worthy successor to the 750-km-range K-15 (also known as the B-05), India's first undersea missile, and extends India's strike range substantially," acknowledged sources in the Defence Research and Development Organisation (DRDO), which is fostering India's weapons programme.

The missile was fired from an underwater pontoon off India's eastern seaboard at a simulated target in the Southern Indian Ocean. "The full range of this twin-stage missile was validated," sources confirmed to The Sunday Guardian.

The K-4 is a critical component of the missing third (or underwater) leg of India's nuclear triad of weapons, which can be launched from air, land and under the sea. The K series of missiles is named after the missile stalwart and former President A.P.J. Abdul Kalam.

"With the K-4, India's underwater deterrence becomes more meaningful. The present range (750 km with the earlier K-15, India's first undersea missile) is hardly deployable," infers veteran submariner and nuclear strategist Rear Admiral (Retd) Raja Menon, who sees the K-15 mainly as a stepping stone in the learning curve for the development of long-range submarine-launched ballistic missiles. The K-15 has been test-fired earlier at least 10 times. The enhanced range of the K-4 will give India better stand-off attack capability without having to get too close to the target, which involves big risks.

Underwater deterrence based on proven capability to fire nuclear-tipped missiles from a submarine is critical to India's doctrine of No First Use. This is considered the most reliable, and survivable, second strike capability because nuclear weapons hidden under the sea are the most difficult for an adversary to target in a decapitating attack. Although the land-launched Agni-4 and Agni-5 give India's nuclear weapons a greater reach of up to 5,000 km and beyond, unique technological challenges had to be overcome in the development of the K-4, which makes Indian deterrence more credible.

But despite this impressive breakthrough, India's undersea missiles are not deployable weapons yet. These have to be first mated with the Arihant class of nuclear-powered submarines being developed by India. Arihant, the first of the three nuclear submarines (SSBN) being built at Vishakhapatnam, is being readied for sea trials soon. Its nuclear reactor turned critical last year.

The Arihant and the two follow-on submarines will reportedly be able to carry 12 K-15 or four K-4 missiles. These missiles will finally be proven in test-firings from the Arihant during weapons trials, which are to follow sea trials later this year. Former Navy chief Admiral D.K. Joshi had publicly indicated last year that the Arihant would be on operational deterrence patrol by the end of 2014, but further deadline slippages on this already-delayed programme appea inevitable.

The good news is that the weapons of underwater deterrence appear ready, even as the platform which will carry these through oceanic depths is crossing the final hurdles.