Watch Christopher Nolans Harrowing, Hopeful Dunkirk Trailer

Director Christopher Nolan has unveiled his harrowing but hopeful trailer for Dunkirk, a film about the 10-day-long World War II battle and evacuation in the French city in 1940.

Following its teaser in August, the two-minute preview of the war flick shows the great lengths Nolan went to ensure the realism of the bloody, massive mission, where 400,000 Allied forces faced 800,000 Nazi troops. In the opening moments, the intimidating propaganda the Nazis used to taunt the Allies is shown falling from the sky.

Dunkirk stars Kenneth Branagh, newcomer Fionn Whitehead, Mark Rylance and Nolan stalwarts Tom Hardy and Cillian Murphy; the former plays a pilot in Dunkirk, while the latter portrays a sailor who survives a submarine attack, only to be rescued and brought to the fight in Dunkirk. Theres no hiding from this, son, Murphys character is told.

One Directions Harry Styles, making his big-screen debut, is also shown briefly in the trailer as part of a group of young soldiers witnessing the carnage unfolding around them.

Dunkirk arrives in theaters on July 21st.