"The script is excellent. When I read the script, I decided that I would do it even for free and this is actually what I have done," Manoj, 43, said here Thursday at the music launch of the film.
"It is a hard-hitting film that tells the story of our country. It won't let the viewers lose their attention even for a second. The entire cast and the script are the USP of the film," he said.
Co-produced by Kashyap and Sunil Bohra, it is releasing Oct 12.
Based on actual events of 1930 Chittagong Uprising, the film is directed by former NASA scientist Bedabrata Pain.
"Chittagong" talks about little-known incident in the 1930s British India, where a handful of untrained teenage boys and girls, led by a school teacher, gave the British their first military defeat.