Book excerpt: This military history offers a provocative take on the “Special Relationship” between the UK and the USA from the close of WWI into the Cold War. After the Great War, the American government contemplated what it would mean to pursue global superpower status. One potential consequence might have been conflict with Great Britain. And so, the US drew up War Plan Red: a scheme by which American forces invaded Canada and the Caribbean, drawing the Royal Navy into North American waters—and leaving the rest of the British Empire vulnerable to attack. In 1939, the American military created an intelligence-gathering machine within their Embassy in London under Ambassador Joe Kennedy. Two years later, the US Army Special Observer Group traveled to Britain to plan for Anglo-American cooperation should the United States enter World War II. Their intelligence-gathering activities spread out as far as the Middle East, Africa, South America, Russia, and Asia—far beyond the terms of the original brief. At the start of the Cold War, a whole new range of subterfuge was initiated by the CIA. So, were the Americans allies or spies? In this enlightening study, acclaimed military historian Graham M. Simons examines how two of history’s greatest allies could find themselves in bitter conflict.