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THE DEFENCE of the United Kingdom is a wide subject. Hitherto no official historian, at least in recent times, has approached it from an inter-service viewpoint. In apportioning my space between its various aspects, in deciding what to include and what to leave out, I have had no modern precedent to guide me. I have made my own choice within the framework of limitations necessarily imposed on a contributor to a series of inter-related volumes, and with valuable assistance from the Editor and his Advisory Panel of senior officers drawn from all three fighting Services. I have been given full access to official records, but in making use of them have respected the requirements of military ‘security’ and the constitutional principle which forbids discussion of individual differences of opinion within Cabinets or disregard of Civil Service anonymity.

During the Second World War three great dangers confronted the United Kingdom. The first was starvation through severance of our sea communications—a potent threat to a country long accustomed to import much of its food and to pay for it largely from the proceeds of an export trade involving a constant outward flow of manufactured goods and an inward flow of raw materials. The second danger was invasion, which came nearer in 1940 than at any time since the Napoleonic Wars, or perhaps, if we disregard the bloodless landing of William of Orange in Tor Bay, since the perilous days of the Armada. The third danger was air attack. At no stage did bombing seriously threaten the country with defeat through collapse of the national will to fight; but in 1940 the German air force made a formidable attempt to crush the air defences as a prelude to invasion—or even, as some of our opponents hoped, to the unopposed occupation of a land already subjugated by Reichsmarschall Göring and his airmen.

At the outset of my task it was made clear to me that I should be expected to give little space to the defence of ocean trade in view of a decision to devote a number of volumes to the war at sea. I have willingly left it to a naval colleague to review, with expert knowledge, the progress of the struggle against the submarine, the surface raider and the long-range ocean-going aircraft. Inevitably I have made some references to these matters; and I am grateful to Captain Roskill for showing me parts of his draft and reading parts of mine. These references are, of course, much briefer and less numerous than they would have been but for the decision to treat the war at sea as

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a separate subject. It would be regrettable if their brevity and rarity were thought to imply that, in the opinion of any responsible historian, the defence of ocean trade can safely be ignored by strategists concerned with the defence of the United Kingdom. In fact no aspect of home defence, in the widest and best sense of that term, has been more important in modern times.

Defence against invasion is likewise a field where the interests of the historian of home defence may impinge on those of the naval historian. Just as one of the two great tasks traditionally devolving on the Royal Navy is to protect the merchant shipping which links Britain with the outside world, so the other is to challenge any attempt to land a hostile force on these shores. Both are strategically offensive, although often they provide opportunities for offensive tactics. A measure designed to serve one of these purposes frequently serves the other also. Destroyers and aircraft watching off the East Coast for an invader, battleships and cruisers chasing commerce-raiders in the South Atlantic, ships of the line engaging the enemy in Aboukir Bay or off Cape Trafalgar may alike, in the eyes of a strategist to whom the seas are one, be engaged in defence of the home country. But a writer on home defence may need to accept a narrower definition of his province. In practice I have suffered no hardship from this restriction. Notwithstanding the impossibility of drawing a continuous line of demarcation between defence against invasion and the defence of trade, it was always clear that many naval measures, related to home defence in its wider interpretation, might be touched upon in the present volume but could be best described at length elsewhere, and that others—including some whose manifest aim was home defence in the narrower sense—ought to be regarded as common ground.

Accordingly the knowledge that naval measures to resist invasion were not my exclusive province has not debarred me from treating them at such length as I have thought appropriate. If my treatment appears more summary than the traditional role of the Royal Navy as the country’s prime defender against an assailant who comes by sea may seem to warrant, the reason is simply that I have judged it unnecessary, and even undesirable, to dwell long on that aspect of my subject. The essence of naval planning is that plans should be elastic. To give more prominence than I have given to measures contemplated, at one stage or another, by the Admiralty and naval Commanders-in-Chief for the reception of an invasion fleet that never sailed might have been misleading. What shape would have been assumed by such naval actions as might have followed the sailing of that fleet, who can say? Perhaps the one assertion that can be made with confidence is that it would not have conformed to preconceptions which the wisest did not allow to take possession of their minds.

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In the outcome the issue of invasion or no invasion was decided not at sea but in the air. It is conceivable that, if the Luftwaffe’s attempt to gain air superiority over southern England and the English Channel had succeeded, Hitler might still have hesitated, as did his predecessors from Parma to Napoleon, to trust his transports to waters not commanded by his fleet. More probably he would have chanced his arm as he did in Norway, France and Russia. What is certain is that the victory won by our air defences deprived him of all choice.

While, therefore, I have given a good deal of my space to the enemy’s preparations to land troops in this country and—with the proviso made above—to steps taken by the Royal Navy and Home Forces to oppose them, I have given still more to air attacks on the United Kingdom and corresponding measures of air defence. If the Battle of Britain was not the most important action ever fought by British arms—and posterity may well deem it so—its effects were certainly no less momentous than those of the most striking victories of Hawke or Nelson. I have thought it right to review the battle in some detail, and no less desirable to sketch, against the background of political events, the period of preparation that began with the adoption of a scheme of air defence soon after the end of the First World War.

Strategically, the succession of night attacks on this country which began before the daylight battle was well launched and continued almost until the end of the war with Germany was less important. A German victory in the daylight battle might have made the United Kingdom indefensible; the night ‘Blitz’ and its aftermath never brought the enemy within sight of inflicting a decisive stroke. But the raids had such profound and memorable effects on the fives of most of us that to slight them would have been a blunder. The flying bomb and the long-range rocket failed, in their turn, to bring much comfort to the enemy ; but their novelty, their challenge to the ingenuity of those called upon to assess and act upon the threat they offered, their potential value to an enemy more favourably placed than were the Germans by the time they brought them into use, all qualify them for much more than passing mention. Some account of their early development seemed essential; and here I was fortunate in having access not only to much published and unpublished material about the rocket but also to new matter kindly laid before me by Dr. Fritz Gosslau, who was closely associated with the birth and progress of the rival weapon.

Civil defence is the subject of a volume with that title, contributed by Major Terence H. O’Brien to the United Kingdom Civil Series of official histories edited by Sir Keith Hancock. I have therefore made only brief references in my volume to civil defence matters,

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notwithstanding their obvious relevance to my subject. Major O’Brien generously allowed me to see his book while it was yet unpublished; he also read the draft of some of my chapters and shared with me his knowledge of certain facts and figures of interest to both of us.

Unpublished documents have provided the bulk of my sources and have been placed unreservedly at my disposal. Detailed citation in a published volume of documents not generally available for study would serve no useful purpose even if it were desirable on other grounds; for the benefit of students who have access to the sources references are given in a limited number of copies which such readers will be able to consult. Nevertheless I must record here my particular debt to the authors of certain monographs and narratives prepared in the Cabinet Office Historical Section and the Air Historical Branch of the Air Ministry under the direction of Brigadier H. B. Latham and Mr. J. C. Nerney respectively. Mr. Nerney and his staff have been indefatigable in searching the records on my behalf and he has given me much help and encouragement. For valuable comments and for checking certain facts and figures—for whose accuracy, however, I alone am answerable—I am grateful to Rear-Admiral R. M. Bellairs of the Historical Section of the Admiralty, to Brigadier Latham and Mr. Nerney and to many other officers and officials, some of them unknown to me, in various departments of the administration. My task would have been impossible without the generous help of Mr. Brian Melland of the Cabinet Office and Squadron Leader Louis Jackets of the Air Historical Branch, who have sought out and translated or digested for my benefit a vast mass of material. I owe thanks, too, to others who have worked under their supervision, and in particular to Mr. R. R. A. Wheatley for a paper on German invasion plans, on which I have drawn in Chapters XI and XIV.

I have had the advantage of receiving comments and suggestions from Commanders-in-Chief, Chiefs of Staff, members of wartime governments and other actors in my story who very kindly read my drafts in whole or part. I cannot sufficiently express my gratitude to them for the generous gift of their time and special knowledge. Several of these commentators, and also some distinguished wartime leaders who had no opportunity of reading my drafts, were good enough to discuss points with me and give me the benefit of their experience. Such contributions did much to amplify, and sometimes correct, impressions drawn from documentary sources or from observation at a less exalted level. These generous helpers do not, of course, share the responsibility of Editor and author for statements made and views expressed. If I do not mention here the names of most of them, it is because I believe they would rather rest content with

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private gratitude than figure in a list whose length might tire the reader’s patience. Even so I venture to record my appreciation of the pains taken to elucidate particular topics by Lord Hankey, Field-Marshal Lord Ironside, General Sir Bernard Paget and Lieutenant-General Sir John Swayne.

Reference is made in footnotes to published works in rare cases where such material has been relied upon as a primary source, or where courtesy demands that course. I apologise to any authors whose brains I may unwittingly have picked without acknowledgement.

The sources of the illustrations are given in the appropriate list. To all those concerned I tender thanks. For providing most of the photographs I am indebted to the Director General of the Imperial War Museum, and for doing much to guide my choice to the Deputy Director, Mr. A. J. Charge. The maps were drawn under the direction of Colonel T. M. M. Penney of the Cabinet Office, who has been most helpful.

My biggest debt is to the Editor.

B. C.

Falmer, Sussex.

22nd October 1956