On May 19, 1940, newly-appointed British prime minister, Winston Churchill, was editing his first speech to the public. With minutes to go before the microphone went live, Churchill was dictating edits to his typist and marking up his printed speech. It’s one of many great scenes in the new movie, Darkest Hour. I recently spoke to producer/screenwriter Anthony McCarten about the movie’s message: A great leader skilled in the art of communication can unite a nation.

McCarten is a wordsmith who also wrote the highly acclaimed film about Stephen Hawking called The Theory of Everything. For Darkest Hour, McCarten chose to center the film around four crucial weeks of World War II when a leader’s words did, indeed, ignite the spirit of a nation.

“Is it valid to say that if it had not been for Churchill’s skill as a communicator, the world would have been a far different place?” I asked.

“You can back up that argument,” says McCarten. “Before Churchill had done anything else, he was a writer. He believed to the core that words matter. They count. They can change the world.”

Few people know how close England came to making a ‘peace’ deal with Adolf Hitler in May of 1940. The public and many of the most influential members of the British Parliament favored appeasement with Nazi Germany. The Netherlands, Belgium and France had fallen to the German army. Hundreds of thousands of British and Allied troops were isolated at Dunkirk in Northern France. England was the next target.

In the film, we see Churchill—played magnificently by actor Gary Oldman—isolated, fearful and doubting his own position. But when Churchill put words to paper and spoke them out loud, everything changed. One of the best lines in the movie captures Churchill’s greatness: “He mobilized the English language and sent it into battle.”

In three speeches over the course of a month, Churchill turned around public opinion and gave the British people the courage to fight. Churchill’s speeches in Darkest Hour provide a master class in communication for any CEO or leader who wants to move people to action.

The one word mission statement. On May 13, 1940, Churchill addressed the House of Commons in what’s become known as the “Blood, Toil, Tears and Sweat,” speech. In it, Churchill poses a rhetorical question.

“You ask, what is our aim? I can answer in one word: Victory. Victory at all costs. Victory in spite of all terror. Victory, however long and hard the road may be, for without victory there is no survival.”

“If you look at the copies of Churchill’s speeches that have survived, they are heavily marked up,” McCarten told me. “He was scrupulous about the impact of each word. He preferred short words and the repetition of short words. He knew everything about the techniques of rhetoric.”

Reframe the narrative. Historically, Dunkirk was a defeat. Small boats were mobilized by the British government to pick up 338,000 troops stranded on the coast of Northern France and carry them back across the English channel. The movie, Dunkirk, captures the harrowing escape. But rather than speak the words of defeat, Churchill reframed the event and turned it into call to arms.

On June 4, 1940, Churchill gave one of the most stirring speeches of the twentieth century. “We shall go on to the end,” he resolved. “We shall defend our Island, whatever the cost may be; we shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields and in the streets, we shall fight in the hills; we shall never surrender.”

Some members of parliament who heard the speech live were said to be in tears. Churchill used all of the rhetorical devices of classic literature to deliver one of the greatest speeches in history. And he kept the words simple. For example, each word in this sentence is no more than one syllable: “We shall go on to the end.” Once again, Churchill chose short words on purpose. According to McCarten, the “fighting on the beaches” speech took a very nervous and fearful country and galvanized them into accepting their destiny to fight on.”

Exude optimism in words and actions. Churchill was a great editor. In the final of the three speeches delivered on June 18, 1940, he had his typist make changes to the 23-page script up until the final few minutes. The British had resolved to fight. Churchill reminded them what they were fighting for. “Let us therefore brace ourselves to our duties, and so bear ourselves that, if the British Empire and its Commonwealth last for a thousand years, men will still say, ‘This was their finest hour.’

If you search for historical photos of Churchill in May and June of 1940, you’ll see that in many public photographs he’s making the V sign, for victory. What victory was he referring to? The British hadn’t won yet. But Churchill wanted the British to see themselves as victors. Emotions are contagious and Churchill knew how to channel positive emotions effectively.

The power of words can, and do, shape society. The movie, Darkest Hour, reminds us that through their words, business and political leaders can inspire people to do great things.