Asked whether it was difficult for him to direct a spy film, Grewal said: "It wasn't difficult. I really like spy and espionage thriller films. I feel directing films of this genre comes naturally to me."
The idea for "RAW" struck him while reading about the 1971 war.
"What was the role of people who were spying for the Indian intelligence agency at that point of time? I got fascinated with their stories. I did deep research and felt I should write a story on this subject, and that's how this film happened."
The audience has earlier appreciated Hindi spy films like "Baby", "Ek Tha Tiger", "Raazi" and "Agent Vinod".
What will set "RAW" apart?
"I feel there are still a lot of spy stories, which we haven't seen on the big screen. If you take the India-Pakistan war of 1971, I feel we can still make 20-30 stories from that period because all stories are really interesting.
"I feel every story has its own voice and this story has my own voice and interpretation, which is completely different from earlier spy films we have seen on-screen."
"RAW" stars John Abraham, Mouni Roy, Jackie Shroff and Sikandar Kher in the lead roles. It will be released on April 5.