The subject of this book is Hitler's strategy. I have tried to preserve the distinction between the sphere of strategy and the sphere of operations, and have wished to deal only with the former. Thus Hitler's share in the conduct of operations, in the execution of his plans, figures hardly at all in the book; and the main emphasis throughout is on the formulation of his central or inter-theatre plans for the strategy of the war as a whole.

I have set myself a second limitation by confining my use of evidence to contemporary documents as far as possible. I think it will be agreed that there is some merit in this approach if the documents can stand on their own, without the support of evidence which, however reliable, is less authentic; and I hope to have shown that they can.

It is as a result of this approach that I have been able to give more detailed attention to naval subjects and opinions than to others, for the most important and complete series of documents available on the subject happens to be among the captured German naval records. But, as will be obvious enough, I have not limited myself to the evidence of the naval records. On the contrary, whenever it was relevant to the subject of Hitler's strategy, or to other points raised by a study of the naval archives, I have incorporated the evidence of any non-naval documents on which I could lay my hands. All the documents presented at the Nuremberg Trial have been sifted with this end in view, and these have provided most of my accessory material; but other collections of documents have occasionally been pressed into service. The chief sources used are described in more detail in the following Note on Sources and References.

For all these attempts to offset it, the naval bias remains; it may be argued that it leads to a somewhat arbitrary and incomplete treatment of the subject; but, apart from the fact that the naval evidence is so complete that it ought to enable a balanced view to be taken, there is, I submit, another reason why this approach can be followed without too much risk of distortion.