In Britain, unemployment, which had risen to two million after the war, fell to a million, and overseas investments rose to near-prewar levels. People forgot their troubles and lost themselves in a new dance craze, the Lindy Hop, or in new fads such as the crossword puzzle and a Chinese game called mah-jongg. Then, on October 29, 1929, Wall Street crashed. A week later the economist John Maynard Keynes reassured Britons that “there will be no serious direct consequences in London resulting from the Wall Street slump.” He was wrong.

A good case can be made that 1931, the year Japan invaded Manchuria and the Depression reached full force, marks the end of the post–World War One era and the beginning of the pre–World War Two era. On one side of the date lay the Locarno and Kellogg-Briand Pacts and the sunlit uplands of collective security and disarmament; on the other side, the howl of the approaching whirlwind. In 1932, Oswald Mosley founded the British Union Fascists, the unemployment rate in Britain rose to 2.5 million, and the streets of Europe filled with thousands of men, hardened by war, disillusioned by peace, impoverished by the slump, and possessing loyalties—to Nazism, Fascism, communism—that transcended national borders. In 1933, Hitler came to power and Germany and Japan walked out of the League of Nations and the World Disarmament Conference. Less noted but also significant, in 1933 the British Chiefs of Staff issued their first warning about a new European war. “Germany is not only starting to rearm, but . . . she will continue the process until within a few years hence she will again have to be reckoned a formidable military power. . . . It would therefore seem that anywhere in the next, say, three to five years, we may be faced with military demands for an intervention on the Continent.” To deter the Germans, the chiefs recommended the creation of a British expeditionary force.

The politicians were horrified. The previous February, the Oxford Union had overwhelmingly carried this motion: “This house would not in any circumstances fight for King and Country.” Then in October—the same month the Chiefs of Staff issued their warning—a Labour candidate running on a platform of unilateral disarmament won a by-election in the reliably Conservative London constituency of East Fulham. A quarter of a century later, in his memoir The Gathering Storm, Winston Churchill still sounded astonished by the East Fulham result.

In 1934, the Chiefs of Staff again unsettled the politicians by urging the creation of a British expeditionary force capable of fighting a Continental enemy. First and foremost, Never Again meant no British soldiers on European soil. Even the famously bellicose Churchill balked at such a prospect. The last time Britain sent an expeditionary force to the Continent, nearly seven hundred thousand men had not come back. Furthermore, Churchill, like many other politicians who kept current with advances in military technology, did not see the need for such a force. Airpower, not ground power, would dominate the battlefield of the future.

Gas bombs, chemical bombs, sky-darkening bomber streams: in the interwar years, the air threat was viewed in the same apocalyptic terms as the nuclear threat is today. “Our cities will be rendered uninhabitable by chemical bombs. . . . We are faced with the wipeout of civilization,” declared an authority on aerial warfare. Films such as H. G. Wells’s Things to Come put images to the warnings. For a score of weeks in hundreds of British theaters, fleets of bombers throbbed across the gray English sky; beneath their noteless drone cities exploded, people exploded, fire and black smoke flared from the holes where Parliament and St. Paul’s had stood; civil defense workers tagged bodies in public parks, the underground collapsed on screaming passengers, and millions of refugees clogged the roads. A secret report compiled for the British government estimated that in the first two months of a new war bombing would produce 1.8 million casualties, including 600,000 dead.I

As airpower came to dominate the rearmament debate, a tortoise-and-hare contest developed. The hare was Churchill, quick-thinking, quick-speaking, quick-acting; the tortoise, Stanley Baldwin, the leader of the Conservative Party and three-time prime minister. No one had ever called Stanley Baldwin quick at anything. At Cambridge, he was asked to resign from the debating society because he never spoke. The prime minister’s chief attribute—indeed, his critics would say his only attribute—was likability.