The Arihant Watershed

India recently took its first steps towards establishing the third leg of a nuclear triad: the ability to launch nuclear weapons from under the sea.

- Sandeep Unnithan

On November 5, Prime Minister Narendra Modi announced that India’s first indigenous ballistic missile submarine (SSBN), the INS Arihant, had completed its first deterrent patrol.

A strategic deterrent patrol is one where an SSBN with a full complement of nuclear-tipped missiles sails towards its intended area of deployment and within range of an adversary’s targets. In case of an attack by a nuclear-armed adversary, India’s Nuclear Command Authority (NCA) can order the submarine to launch its weapons.

The prime minister’s statement assumes significance because it also hints at having established a command chain—the NCA’s ability to communicate with a submarine lurking in the depth of the ocean. In the Arihant’s case, the order will be passed via a sophisticated Extremely Low Frequency (ELF) communication system near Tirunelveli in Tamil Nadu. The Arihant returned to its base in