India has quietly completed its nuclear triad by inducting its first indigenously constructed nuclear submarine ‘INS Arihant’ into service.

On Tuesday, the Indian Defence Ministry sources confirmed that the 6,000-tonne submarine was commissioned by Navy Chief Admiral Sunil Lanba in August. Sources said that they took time to make an official announcement in this regard as the Prime Minister’s Office (PMO) asked the ministry to maintain secrecy because of security purposes.

The induction of INS Arihant gives India the capability to respond to nuclear strikes from sea, land and air-based systems. The submarine also gives second-strike capability to the South Asian powerhouse that has a clearly declared policy of “no first-use” of nuclear weapons.

The Defence Ministry has thanked Russia for helping India in constructing the vessel’s miniaturised nuclear reactor. In a statement, the ministry said that the Defence Research and Development Organisation (DRDO), the Department of Atomic Energy, the Submarine Design Group of the Directorate of Naval Design and some private companies jointly built the submarine under the supervision of the PMO.

The submarine’s design is based on the Russian Akula-1 class submarines and its 83MW pressurised water reactor has been built with significant Russian assistance. Even, the Russian specialists trained the vessel’s 100-member crew and taught them how to reduce the reactor size to help it fit into the 10m-diameter hull of the submarine.

India has ‘Agni’ ballistic missiles and fighters, like Mirage-2000, to deliver nuclear weapons. However, the underwater leg – SSBNs (nuclear-powered submarines with ballistic nuclear missiles) – was missing. SSBNs, which can operate underwater at long ranges for months on end, are considered as the most potent and difficult-to-detect leg of nuclear triad.

Defence experts describe the Arihant story as India’s four-decade quest. India began its hunt for nuclear submarines way back in the 1970s. In late 1990s, the actual construction of three SSBNs began under secret Advanced Technology Vessel (ATV) project. The first 6,000-tonne ATV – INS Arihant – was launched into water at the ship-building centre in the southern Indian port city of Visakhapatnam on July 26, 2009. Unfortunately, the submarine’s 83MW nuclear reactor went ‘critical’ on August 10, 2013. Later in December 2014, INS Arihant headed for extensive sea trials that included test-firing of K-series of missiles. Finally in August this year, INS Arihant was slated for induction. Meanwhile, the construction of the second nuclear submarine ‘INS Aridhaman’ is virtually completed and it is slated for delivery in 2018.

Koushik Das, based in the Indian capital of New Delhi, is a senior news editor with more than 15 years of experience. He also runs a blog - Boundless Ocean of Politics. E-Mail: [email protected]