This work considers, for the first time, the intelligence relationship between three important North Atlantic powers in the Twenty-first century, from WWII to post-Cold War.

During the second half of the 20th century, intelligence co-operation between the three North Atlantic powers of America, Britain and Canada played a vital role in Western struggles against Nazi Germany, Imperial Japan, Soviet Russia and their lesser allies.
As demonstrated in the case studies in this volume, World War II cemented loose and often informal inter-allied agreements on security intelligence that had preceded it, and created new and important areas of close and formal co-operation in such areas as codebreaking and foreign intelligence.
But what was the true nature of this co-operation? Wartime myths have obscured much of the rality, and while the western powers undoubtedly benefited from the dividends of these agreements during the Cold War that followed, they also experienced restrictions on national sovereignty whose costs have often caused controversy, while the search for co-operation frequently provided cause for friction.