This book provides the first history of the British and American Intelligence Divisions (IDs) in occupied Germany and the liaison between them. It reveals that after the fall of Adolf Hitler’s Third Reich, much of Germany was controlled by an Anglo-American secret system of rule which was the real backbone of the occupation and largely explains its successful outcomes. Based in Heidelberg, the American ID was the senior American military intelligence organisation in occupied Germany, responsible for the security of American forces in Europe. The British ID, based in Herford, was a purpose-built intelligence organisation designed to ensure the security of the British Zone of Germany and to help achieve the Allied occupation objectives. The IDs undertook military, scientific, security, political, and state-building intelligence tasks which each form the focus of a chapter in this book.