The model for this is the defence department's "open" but barely publicised relationship with Hollywood. The Pentagon, for decades, has offered film-makers advice, manpower and even hardware - including aircraft carriers and state-of-the-art helicopters. All it asks for in exchange is that the US armed forces are made to look good. So in a previous Scott film, Black Hawk Down, a character based on a real-life soldier who had also been a child rapist lost that part of his backstory when he came to the screen.

Dustin Hoffman film showed how to run a war from a Hollywood studio.