The main reason for anyone working in the field of intelligence history is to locate and place in perspective what has been described as the missing dimension of modern history: the role intelligence played in forming and executing policy in reaction to the great issues of the past one hundred years.

Until quite recently this has not been possible, because intelligence agencies in Western democracies simply did not make public either their archive or (except in some highly regulated manner) their history: indeed until the early 1990s the British intelligence community operated under the royal prerogative and had no legal or corporate existence. So, as historians were reliant on official histories, all they could glean were tantalising glimpses of events. In the circumstances of official denial, the very idea of creating an intelligence history series would have been frankly absurd. With few scholars working in this field and the governments of western democracies continuing to guard their secrets well, few intelligence files, even from the distant past, ever got to see the light of day in public archives. It was in this vacuum that ex-intelligence officers, such as Ian Fleming and John Le Carré, wrote sensational fictionalised accounts of life in intelligence communities. These gave journalists writing about current intelligence matters the reliable fallback of starting a newspaper article with some kind of James Bond or George Smiley reference. Scholars were forced to rely for their sources on personal contact, secondary material and memoirs. As a result, though some works were and remain excellent studies, providing the foundations upon which modern scholarship can be based, much of what was written we can see today as largely an antiquarian study of intelligence.

However, much has changed recently, during a period which saw the end of the Cold War and the opening up of government secrets to public scrutiny via freedom of information legislation. In nations like Britain and the United States, both scholars and the public have, for the first time, gained access to information that in its day was considered the most secret and sensitive.