INS Arihant, India's first nuclear ballistic missile submarine, has completed its first deterrence patrol, Prime Minister Narendra Modi said today. "I congratulate all those involved, especially the crew of INS Arihant for this accomplishment, which will always be remembered in our history," PM Modi said. The 6,000-tonne INS Arihant, under development for three decades under a highly classified programme, comes under the direct control of the Nuclear Command Authority headed by PM Modi.