INS Arihant was commissioned by Navy Chief Admiral Lanba in August.

India has quietly completed its nuclear triad by inducting the indigenously built strategic nuclear submarine INS Arihant into service.

INS Arihant was formally commissioned by Navy Chief Admiral Sunil Lanba in August, defence sources confirmed to The Hindu on Monday. The issue was reported earlier in the day by TV channel NewsX.

To maintain secrecy, it is not being referred to as INS Arihant, sources added. INS which stands for ‘Indian Naval Ship’ is affixed to a ship only after it is inducted into service.

Arihant is capable of carrying nuclear tipped ballistic missiles, the class referred to as Ship Submersible Ballistic Nuclear (SSBN). SSBNs are designed to prowl the deep ocean waters carrying nuclear weapons and provide a nation with an assured second strike capability — the capability to strike back after being hit by nuclear weapons first.

Second strike capability is particularly important for India as it had committed to a ‘No-First-Use’ policy as part of its nuclear doctrine.

The vessel weighing 6000 tonnes is powered by a 83 MW pressurised light water nuclear reactor. The project to build a strategic vessel began as the Advanced Technology Vessel (ATV) project in the 1980s and the vessel was launched in 2009 by Prime Minister Manmohan Singh. Since then it was put to extensive sea trials and the reactor on board went critical in 2013.

It will be armed with the K-15 Sagarika missiles with a range of 750 km and eventually with the much longer range K-4 missiles being developed by the Defence Research and Development Organisation.

With this India joins the select group of countries which have a nuclear triad, i.e. capable of delivering nuclear weapons by aircraft, ballistic missiles and submarine launched missiles.

Both the Defence Ministry and the Navy declined to comment as the issue is out of their purview being a strategic asset.