The trailer for Christopher Nolan's new movie Dunkirk is really depressing

He may have taken the superhero genre down a dark and gritty path, but Christopher Nolan's new movie looks to be his most depressing yet.

The full trailer for Dunkirk is out, with the Batman director's new movie telling the true story of the evacuation of Dunkirk at the start of World War II, when British and French troops found themselves surrounded by German forces.

"The enemy tanks have stopped. Why waste precious tanks when they can pick us off from the air like fish in a barrel?" one officer says near the beginning of the trailer, setting the movie's dark tone.

Though it has a stellar cast that includes Kenneth Branagh, Mark Rylance and Tom Hardy, the focus is on younger soldiers experiencing the horror of war for the first time.

The young leads include Jack Lowden, Fionn Whitehead, Aneurin Bernard and former One Direction member Harry Styles.

We don't know the name of Styles' character yet, but we know his character will face peril, as there is a brief shot of him drowning in the French sea.

The trailer makes it clear this will be a full-on war movie, with countless shots of exploding boats, gunfire, planes chasing each other through the sky and dead soldiers strewn across beaches.

We will have to wait until July 20 to see if The Dark Knight director's latest effort is as grim as the trailer, but knowing Nolan, it is sure to be one epic movie regardless.