Andrew Roberts had unprecedented access to the diaries of King George VI, who during World War II met every Tuesday with Winston Churchill.

In Churchill: Walking With Destiny—rated by The New York Times as the best one-volume biography of Winston Churchill yet written—British author and historian Andrew Roberts explores seemingly well-trod territory. More books have been written on the celebrated British prime minister than any other 20th-century figure, with the exception of his nemesis Adolf Hitler. But Roberts’ work, based on extensive new material from King George VI’s diary and wartime meeting notes, brings to light a more multifaceted character than ever before. Roberts charts Churchill’s many trials and tribulations as he emerged from “the wilderness” to become Britain’s symbol of courage and defiance in World War II. In his interview with Military History the author elucidates why the world still needs—and has much to learn from—Churchill.

Of the many biographies of Churchill, what makes Walking With Destiny unique?
The new sources I found. Queen Elizabeth allowed me to be the first Churchill biographer to use her father’s extensive and detailed diaries. King George VI met Churchill every Tuesday of the Second World War. Churchill trusted him with all of the great secrets of the war, and the king wrote everything down. I was very fortunate to have this exciting new source. Forty-one sets of papers also have been deposited at Churchill College, Cambridge, since the last major biography of Churchill.

‘Churchill the military historian was able to talk about the times Britain had been in the same kind of danger yet had wound up being victorious. He was able to boost Britain’s morale in a way that was quite exceptional’

How did Churchill’s early military experiences affect his performance as wartime prime minister?
They were crucial. He went to [the Royal Military Academy] Sandhurst and fought in five campaigns on four continents, and his experience in the trenches in the First World War were very important as well. The day he became prime minister he said, “All my past life has been but a preparation for this hour and for this trial.”

That was specifically true when it came to military history. He’d been thinking about it, he’d been writing about it, he’d been immersed in it and fascinated by it for 40 years. As a result, he ensured that the men on the front line were taken care of, that there should be fresh bread, a postal service that worked so they could be in touch with their loved ones, things like that. Doing such things was absolutely instinctive to Churchill, because he had been on the front line himself.

How did his generals react to his military advice to them?
They tended not to like it, of course, because generals don’t want to be told by politicians what to do. Churchill wasn’t going to make the same mistake made in the First World War, where overmighty soldiers and sailors like Admiral John Fisher and General Douglas Haig and Field Marshals William Robertson and Herbert Kitchener became more powerful than the civil leaders and the politicians and statesmen. That’s why he made himself minister of defense as well as prime minister in May 1940, and why he ensured he chaired the defense committee of the War Cabinet, which met so very often with the chiefs of staff to plan operational policy.

He had clashes with Field Marshal Alanbrooke, chief of the Imperial General Staff and, from March 1942, chairman of the British Chiefs of Staff. Churchill never overruled him. But policy was made through the creative tension between these two men.

In wartime Britain the irrepressible prime minister balances his top hat atop his walking stick as daughter Mary looks on. (Photo 12, Fox Photos (Getty Images)

To what extent did Churchill’s oratorical skills motivate Britons during World War II?
They were transformational. Britain went into the war with no great enthusiasm. It was only a generation after the bloodletting of the Great War. There were no celebrating crowds in the streets as in 1914. After the disaster at Dunkirk, where the British Expeditionary Force was forced off the Continent, it would have been easy for a mood of defeatism to have crept over Britain. There were people like Lloyd George, the previous prime minister, who wanted to make peace with Hitler.

Churchill’s oratory—the great “We shall fight on the beaches” speech on June 4, 1940, the “This was their finest hour” speech of June 18 and many others—encouraged the British people to realize they had been there before. Churchill the military historian was able to talk about the times Britain had been in the same kind of danger yet had wound up being victorious. He was able to boost Britain’s morale in a way that was quite exceptional.

Did his personal example have a similarly salutary effect?
Yes, that was tremendously important as well. Hitler never visited a bombed household or town or city. Churchill did. He went out to the East End, toured the bombed areas, and he used this as a morale-boosting thing to do, which is quite extraordinary. He went to the places where the Luftwaffe had ostensibly been successful and turned it into a propaganda victory for Britain.

Despite his brilliant performance, he was ousted at war’s end. How did that affect him?
He was crushed by it initially; it seemed an appalling personal rejection. On the actual day it happened, when it was clear there was a landslide defeat in the offing, his wife, Clementine, said, “Well, this looks like a blessing in disguise.” Churchill replied, “Well, from where I’m sitting, it looks quite effectively disguised.” But he did come around to appreciating the British people wanted change, and they had been through a lot during the war.

‘He was accused of being a warmonger, and he was ridiculed in the press. Yet he didn’t change his mind’

Which aspects of Churchill’s character do you find most compelling?
His moral and physical courage. There are plenty of people who have one or the other, but relatively few have both. And he most certainly did. In the 1930s, when he took a definite stance against Hitler and the Nazis, he was shouted down in the House of Commons. He was accused of being a warmonger, and he was ridiculed in the press. Yet he didn’t change his mind. And he learned from his mistakes. Relatively few politicians are able to do that. Churchill was, and that was a great strength.

How did Churchill’s relationship with U.S. President Franklin D. Roosevelt affect the course of the war?
It was central. It was tremendously important these two men got on. Immediately after Pearl Harbor Churchill stayed at the White House for three weeks, and he and Roosevelt, along with the American and British chiefs of staff, cobbled together the war-winning strategy. It was an act of tremendous statesmanship on both of their parts and on the part of the people at the War Department who had already been working on this for several years.

Churchill and Roosevelt had a lot in common. They were both aristocrats of their own countries and slightly to the left of politics, so they did see eye to eye. They became close personal friends. Even when the relationship started to break down over political issues in the fall of 1944, you still have a close personal and warm regard that survived until Churchill finally said goodbye to Roosevelt at Alexandria in February 1945.

During a July 1, 1945, visit to occupied Berlin, Churchill pauses outside Adolf Hitler’s ruined bunker to occupy one of the late Führer’s chairs. (Fred Ramage/Stringer/Getty Images)

Is there anything you’ve learned about Churchill that surprised you?
The thing that surprised me most about the new sources I discovered in the various resources I had access to—and the Churchill family allowed me all sorts of access that hasn’t been given to other writers—was the way in which Churchill felt enormous frustration at the United States for not getting more involved in the war before Hitler declared war on the United States on Dec. 11, 1941.

Churchill saw America as the most powerful democracy in the world, understandably, and he very much wanted it to get more involved. But he couldn’t say as much, because it would have provoked great isolationist reaction among the “America Firsters” in the United States. In his conversations with the king, for example, he is critical of the fleet positioning at Pearl Harbor, but of course couldn’t say this to the press or the public or Parliament.

Churchill is known for his wit. Do you have a favorite quote?
Well, they change all the time. Churchill just made so many good jokes—there are about 200 in the book. But nonetheless, yes, there is something very funny: Before the war, when Joachim von Ribbentrop, at that time the German ambassador to London, threatened Churchill at a reception, saying, “You do realize that in the next war Italy will be on the side of the Third Reich,” Churchill replied, “But it seems only fair; we had to have them last time.”

How do you familiarize yourself with the subjects of your books?
Through total immersion in their writings, their diaries and their correspondence, and by just concentrating as much as possible on primary sources. I’m not a great one actually for reading all the secondary sources for people I write about. In Churchill’s case, of course, that would be a completely impossible undertaking, since there are 1,009 biographies of him.

Do you have another book project in mind?
I do. I’ve just signed a contract for a biography of King George III. I am going to attempt to persuade Americans that their last king was not the tyrant of the Declaration of Independence and the current, popular musical Hamilton, but was, indeed, an enlightened monarch. He managed to get the American Revolution entirely wrong, of course, and was extremely unfortunate to live in the same generation as people like George Washington, Benjamin Franklin, James Madison, Thomas Jefferson and James Monroe. Tremendously unlucky of him, really. And, contrary to popular belief, the king did not go mad until after the revolution. MH