INS Arihant is India's first indigenous nuclear submarine

New Delhi: INS Arihant, India's first nuclear ballistic missile submarine, has completed its first deterrence patrol today. This means the submarine is fully operational and, when deployed, for extended patrols, can target regional adversaries such as China with nuclear-tipped submarine-launched ballistic missiles.

Here is your 10-point cheat sheet to this big story:

1. INS Arihant is India's first indigenous nuclear submarine. The Arihant was launched on 26 July 2009, the anniversary of Vijay Diwas (Kargil War Victory Day) by former Prime Minister Dr Manmohan Singh's wife Gursharan Kaur.

2. INS Arihant is armed with four K-4 submarine launched ballistic missile with a range of 3,500 km. 

3. With the first deterrence patrol by INS Arihant completed today, India is ready with its nuclear triad - the capability of firing nuclear weapons from land, air and sea.

4. It can also be armed with 12 K-15 missiles with a range of 750 km.

5. INS Arihant was launched into the water at the ship-building centre in Visakhapatnam and the sea trials were started in December 2014 and the submarine was declared fit for operations in February 2016.

6. INS Arihant is a part of Indian Navy's secretive Advanced Technology Vessel (ATV) project operated under the supervision of the Prime Minister's Office and closely monitored by agencies such as the Department of Atomic Energy and the Submarine Design Group of the Directorate of Naval Design.

7. India has now become part of an elite club of countries - Russia, the US, China, France and the UK that possess nuclear ballistic missile submarines.

8. The 100-member crew of the ship has been trained by Russian specialists.

9. India also operates the Russian-origin nuclear-powered submarine INS Chakra, which it had leased for 10 years from Russia in 2012. This is a nuclear powered fast attack submarine and cannot fire ballistic missiles.

10. Nuclear powered submarines, such as INS Arihant, can deploy underwater for months at a stretch before they need to return to their base to stock up on food and provisions for sailors onboard.