 In December 1971 , during the Indo @-@ Pakistani War of 1971 , the US President Richard Nixon sent a carrier battle group named Task Force 74 , led by the nuclear @-@ powered USS Enterprise into the Bay of Bengal in an attempt to <unk> India . In response , the Soviet Union sent a submarine armed with nuclear missiles from <unk> to trail the US task force . The event demonstrated the significance of nuclear weapons and ballistic missile submarines to then Prime Minister Indira Gandhi . Following the 1974 <unk> Buddha nuclear test , the Director of Marine Engineering ( <unk> ) at Naval Headquarters initiated a technical feasibility study for an indigenous nuclear propulsion system ( Project <unk> ) . 
