This book describes Japan's important role as an ally of Canada and Great Britain during World War One, and how Japan went from being a valued ally to a spurned partner and a potential adversary in the post-war world. In 1921 Canada persuaded the British Empire to end its long alliance with Japan - a decision that would ultimately be fraught with peril for the British Commonwealth in Asia and the Pacific as the world moved toward a second great conflict in the twentieth century.