Early on Tuesday, the Indian Air Force struck a Jaish-e-Mohammad terror camp in Balakot in Mansehra district, the first Indian strike so deep inside Pakistan since the end of the 1971 war. During the Kargil conflict in the summer of 1999, Prime Minister Atal Bihari Vajpayee had instructed the Air Force to stay on the Indian side of the LoC. This is what happened in Kargil nearly 20 years ago. Watch video: India confirms air strike on Jaish-e-Mohammad camp in Pakistan Infiltrators detected On May 3, 1999, some local shepherds reported that armed infiltrators had occupied some 130 outposts on the heights on the Indian side of the LoC. It subsequently emerged that the infiltration had been going on undetected since February that year. Even after they were detected, the Indian armed forces initially assumed the infiltrators were jihadists who could be evicted within a few days. It was only in the second week of May, after more intruders were detected that the Indian Army was able to estimate the scale of the challenge and devise a plan of action to drive out the infiltrators. Express Explained | Mirage, Awacs, Sukhoi, Popeye: How IAF took down Jaish training camp Operation Vijay On May 25, Prime Minister Atal Bihari Vajpayee said all possible steps would be taken to drive out the infiltrators, including the use of air power. The following day, the Indian Air Force launched strikes on the Pakistani intruders. "Once they understood more fully what had transpired along the LoC, the army's leaders responded by moving five infantry divisions, five independent brigades, and 44 battalions from the Kashmir Valley to the Kargil sector, ultimately mobilizing some 200,000 Indian troops in all," the veteran international defence strategies analyst and air warfare specialist Benjamin S Lambeth wrote in a 2012 paper titled Airpower at 18,000: The Indian Air Force in the Kargil War. The objective of the air intervention was to drive out the intruders and restore status quo on the LoC. Operation Safed Sagar In October 2006, Air Chief Marshal Anil Yashwant Tipnis (retd), who was Chief of the Air Staff at the time of the Pakistani incursion, provided a detailed account of the events leading up to the IAF's joining the operations. He recalled that on May 10, a week after the intrusions were first reported, he was intimated that the Army might require some support in Kargil. He later learned that the Army had sought support through Mi-25 and Mi-35 helicopter gunships and armed Mi-17 helicopters in order to evict some armed intruders, but had been advised that the terrain was higher than the effective operating zone of helicopters, and higher authorities would have to be consulted. "Because committing airpower in close proximity to the LoC could dangerously escalate the conflict, Tipnis insisted that the army ‘needed political clearance’ before the IAF could provide the requested fire support,” Lambeth wrote. Tipnis called a review meeting with his most senior officers on May 15, after which the IAF underlined that in the circumstances, helicopters would be "vulnerable in the extreme". Express Explained: Why Balakot is a watershed On May 23, Chief of the Army Staff General Ved Prakash Malik met with Air Chief Marshal Tipnis to discuss the requirement of helicopters. Air Chief Marshal Tipnis noted in 2006 that he finally gave in against his "better judgements". The following day, both the Army and the Air Force decided to take up the matter with Prime Minister Vajpayee. On May 25, Vajpayee chaired a crucial meeting of the Cabinet Committee on Security. General Malik explained to the PM the seriousness of the situation, and the need for the IAF to step in. As Air Chief Marshal Tipnis recalled later, Vajpayee said, "OK, get started tomorrow at dawn." Then came the key question: Could the IAF cross the LoC, the Air Chief asked. Vajpayee is believed to have responded immediately and firmly: "No, no crossing the LoC." As the IAF launched Operation Safed Sagar in support of the Army's ground troops to drive back the Pakistanis, Vajpayee's clear direction remained its guiding principle.