Actor Mark Rylance talks about real-life heroism that inspired "Dunkirk"

Actor Mark Rylance has earned an Academy Award for his portrayal of a Soviet spy in the 2015 movie "Bridge of Spies." 

Now Rylance is back on the big screen in the World War II drama "Dunkirk." The movie focuses on the 1940 rescue of more than 300,000 British and allied soldiers from the beaches of Dunkirk in northern France. 

Rylance plays Mr. Dawson, a civilian who crosses the English Channel in his own boat to help rescue stranded troops from the approaching German army. 

In a conversation on "CBS This Morning," Rylance said he trained for his role by listening to recordings at the Imperial War Museum in London of men who served at that crucial moment in history. 

"The tone of society was different at that time," he explained. "There's a selflessness and they believe in communal effort and togetherness that's a little bit different than England now."  

"They weren't told, of course, by the government that they were going to be bombed and shot at," Rylance added. "They were told there were men who needed to be rescued. It's important to know what your character could know and what might or might not know." 

"Dunkirk" was written and directed by Christopher Nolan. It's getting positive reviews and is considered an early Oscar contender.