Harry Styles talks about making his film debut in Christopher Nolan's Dunkirk and what he learned about the realities of war. Subscribe NOW to The Tonight Show Starring Jimmy Fallon: http://bit.ly/1nwT1aN Watch The Tonight Show Starring Jimmy Fallon Weeknights 11:35/10:35c Get more Jimmy Fallon: Follow Jimmy: http://Twitter.com/JimmyFallon Like Jimmy: https://Facebook.com/JimmyFallon Get more The Tonight Show Starring Jimmy Fallon: Follow The Tonight Show: http://Twitter.com/FallonTonight Like The Tonight Show: https://Facebook.com/FallonTonight The Tonight Show Tumblr: http://fallontonight.tumblr.com/ Get more NBC: NBC YouTube: http://bit.ly/1dM1qBH Like NBC: http://Facebook.com/NBC Follow NBC: http://Twitter.com/NBC NBC Tumblr: http://nbctv.tumblr.com/ The Tonight Show Starring Jimmy Fallon features hilarious highlights from the show including: comedy sketches, music parodies, celebrity interviews, ridiculous games, and, of course, Jimmy's Thank You Notes and hashtags! You'll also find behind the scenes videos and other great web exclusives. Harry Styles Gets Emotional Watching Dunkirk http://www.youtube.com/fallontonight