Although there were generic intelligence reports about infiltration of terrorists into Punjab since the evening of December 31, 2015, the actual story begins post-lunch on New Year's Day when the general intelligence gets crystallised into a specific alert that the target definitely is the Pathankot air base. This is what happens in rapid succession after that:
3 pm: National Security Adviser Ajit Doval convenes a meeting to decide on the next course of action. In attendance are the Army chief, General Dalbir Singh Suhag, the Air Force chief, Air Marshal Arup Raha, and chiefs of intelligence agencies.
6 pm: Army columns start arriving into the air base and get deployed at key locations. Their main task: To secure the air assets in the technical area (fighter aircraft, helicopters, missiles, ammunition dump, etc) and guard the residential quarters that house nearly 3,000 families within the base.
In Delhi NSG teams emplane for Pathankot. They are being pre-positioned in case any hostage situation develops or the terrorists get into houses or built-up areas.
9 pm: The technical area is sealed; NSG gets deployed. The wait and search for terrorists begins. There is no definite information on their exact location.