My history of this history has no ascertainable origin. About forty, perhaps even fifty, years ago I was beginning to think that the last days of May in 1940 may have been decisive for the outcome of the Second World War. This idea, or thought, or perhaps not much more than a sense, accorded with my conviction that the most important phase of the Second World War was the one before December 1941, that is, before the American entry into the war, coinciding with the first German retreat before Moscow—after that, Hitler could still win great battles, but no longer the entire war. From this realization sprang my decision, in 1968, to write a rather large work, The Last European War, 1939-1941, eventually published in 1976. It was during this time, in 1970, that the British government chose to shorten the closed period of most of its papers, from fifty years to thirty. Accordingly I spent a few weeks in London in 1971, mostly at the Public Record Office. I may have been among the first to read and work from the PRO’S cabinet papers of May-June 1940. What I read confirmed my suspicion (if that was what it was) that those days in London were very critical, and not only because of the catastrophic military situation in Flanders and in France — that Churchill’s situation within the War Cabinet was much more difficult than most people, including historians at that time, thought. However, given the scope and the size and the unusual structure of The Last European War, I could devote not more than three pages to this, all of them in part I, the narrative portion of the book.
Sixteen years passed, during which I wrote four or five other books, each about a different topic. In 1989 my then editor and publisher and friend John Herman, of Ticknor & Fields (now defunct), asked me what I might be thinking of writing next. I thought for a while, and said: A book about 1940 – more precisely, about the eighty days from 10 May to 31 July 1940, marked by the duel between Winston Churchill and Adolf Hitler. While writing The Duel I again spent a few weeks in England at the Public Record Office and at some other archives. In The Duel about fourteen or fifteen pages were devoted to the last week of May 1940. And then, seven years after the completion of the manuscript of The Duel, I chose to return to the history of those days, encouraged by the editorial director of Yale University Press, my present publishers. In 1997 and 1998 I returned to London twice for the purposes of my researches, broadened and deepened by reading in a large variety of archives and private papers. Habent sua fata libelli: this is the story of the present book.
Thus it may be said that this book amounts to the completion of a very lopsided trilogy: from three pages in The Last European War to fifteen pages in The Duel and then to two hundred and twenty pages in this one. Or from macrocosmic to microcosmic history, of a sort. A friend said the other day, in mock seriousness, “Will your next book be Three Hours in London?” No, it won’t.
I must now add a caveat. This is that not only the scope but the structures of the abovementioned books are very different. A somewhat uncategorizable historian, I am not a specialist in British political or social or military history. However, one consideration may intrude here. During the past fifteen or twenty years, British historians have written valuable articles and books dealing with Churchill and Halifax and the politics of war, parts of which include those five days in May 1940. At the risk of presumption, I shall venture to say that I have had one advantage over many of them. This has been my knowledge about Hitler—or, rather, my familiarity with documents and other materials relating to him, in this case especially in 1940. For, without understanding what Hitler said and thought and how close he came to winning the war in May 1940, that secondary “duel” between Churchill and Halifax in the War Cabinet seems less important. A flicker of doubt, perhaps; a conflict between two personalities; a footnote in the political history of modern Britain. There were, and are, reasons to look at and treat the five days in London in May 1940 in that way. Such treatments are not necessarily the results of narrowmindedness or excessive specialization. Tightly focused views are often useful, while there is a kind of broad-mindedness that can be flat. In this book, however, I have attempted to combine the narrowing acuity of a specialist with a broader perspective, aware that perspective is a component of reality itself: in sum, that during those five days in London, the danger, not only to Britain but to the world, was greater and deeper than most people still think.