The Battle of Dunkirk remains one of the most legendary and terrifying moments of the 20th century, and the cast of Christopher Nolan's World War II drama 'Dunkirk' got to experience just what that might have been like first hand thanks to the immense detail of the set.

Dunkirk is in theatres on July 20thDunkirk is in theatres on July 20th

Director Christopher Nolan is well known for the astounding scope of his movies, and also that he never does big action scenes by halves. As it goes, 'Dunkirk' is very much one enormously intense action scene for the majority of the running time - and with real World War II spitfires flying around, thousands of extras and genuine explosions, acting wasn't necessary.

'It's not 'pretend there's an explosion happening over here', it's actually going on', says Harry Styles, who plays Alex in the movie in his first ever acting role. 'That just means you get natural reactions to stuff.'

Watch the trailer for 'Dunkirk' here:

Co-star Fionn Whitehead, who plays Tommy, couldn't agree more. 'Any reactions you have are just a response to what's going on around you. It's honest', he insists. 

It actually got to the point where the stars were thinking more about shielding themselves from the chaos that the production team was causing, than about trying to stay in character - indeed, their fear and panic was real a lot of the time.

'I never actually felt like I was thinking about acting', says Tom Glynn-Carney, who plays Peter. 'Because everything was there for you, there was no acting required in many situations.'

Needless to say, these young actors never thought they'd find themselves empathising so closely with the young soldiers who found themselves trapped on that French beach in 1940. 'You can never really put yourself there but that is I think the closest you can come to putting yourself in that situation', says Fionn.

Also starring in the movie are Tom Hardy, Cillian Murphy, Mark Rylance, Jack Lowden and Kenneth Branagh.

More: Watch the full interview from the featurette

'Dunkirk' is set to be released in theatres on July 20th 2017.