May 1940 was a month like no other. The superior German war machine blazed into France, as the Maginot Line, supposedly "as firmly fixed in place as the Pyramids," crumbled in days. With the fall of Holland and Belgium, the imminent fall of Paris, the British Army stranded at Dunkirk, and Neville Chamberlain’s government in political freefall, Winston Churchill became prime minister on this historical nadir of May 10, 1941. Britain, diplomatically isolated, was suddenly the only nation with the courage and the resolve to defy Hitler.

Against this vast historical canvas, Korda relates what happened and why. We first meet him at the age of six, surrounded by his glamorous movie family: his stage actress mother; his elegant father, Vincent, soon to receive an Academy Award; and his devoted Nanny Low, with whom he cites his evening prayers. Even the cheery BBC bulletins that Michael listened to every night could not mask the impending catastrophe, the German invasion so certain that the young boy, carrying his passport on a string around his neck, was evacuated to Canada on an ocean liner full of children.

Such alarm was hardly exaggerated. No one, after all, could have ever imagined that the most unlikely flotilla of destroyers―Dutch barges, fishing boats, yachts, and even rowboats― would rescue over 300,000 men off the beach at Dunkirk and home to England. The miraculous return of the army was greeted with a renewed call for courage, and in the months that followed, the lives of tens of millions would be inexorably transformed, often tragically so, by these epochal weeks of May 1940.