Soon after the Pulwama terror attack, India pulled out its Navy from an exercise and deployed a major part of its fleet, including nuclear and conventional submarines, close to Pakistani territorial waters.During the aggressive deployment of the naval assets by the Indian side, the Pakistanis were getting an impression that New Delhi might use its maritime force to avenge the killing of its 40 CRPF personnel in the suicide bombing in J&K by Jaish-e-Mohammed (JeM).India was continuously keeping an eye on the movement of the Pakistani military but after Indian Air Force hit the Jaish camp in Balakot, one of the most advanced Pakistani Agostaclass submarines — PNS Saad — vanished from the Pakistani waters, a senior government source said.The vanishing act by PNS Saad fitted with air independent propulsion (a technology that allows submarines to stay under water for a longer period than normal submarines) swung the entire Indian Navy into action.“From the location near Karachi from where it vanished, it could reach Gujarat coast in three days and Mumbai in five days. It was seen as a major threat to the security of the country,” the sources said.Soon, anti-submarine warfare specialist warships and aircraft were positioned to help hunt for the missing Pakistani submarine.“All the areas where it could have gone in the given timeframe, extensive searches were carried out by the Indian Navy in areas where it could have gone in the given timeframe. P-8Is were pressed into service to locate the submarine along with the coastal areas of Gujarat followed by Maharashtra and other states,” the sources said.All precautionary measures had been taken by the Navy to ensure that even if the PNS Saad had entered Indian waters, all necessary actions were to be taken to force it to come on the surface, and if required take military punitive action against it, the sources said.As the days progressed, the Indian Navy kept expanding its area of search for the Pakistani boat and satellites were also used to locate it, meanwhile, the force was almost certain that the Pakistanis may have kept it hidden somewhere else.After 21 days of an extensive search, the Navy finally located the submarine on the western side of Pakistan . It was sent there for hiding, to ensure a covert capability in case of extension in hostilities in the aftermath of the Balakot airstrikes.Sources said the Navy is maintaining complete surveillance of the Arabian Sea, especially Pakistani waters, and is aware of Pakistan’s naval activities in the area.