One of the great untold Canadian military stories revolves around the eastern seaport of Sydney, Nova Scotia. Guardian of the Gulf offers a vivid and long overdue account of Sydney harbour's role, and the importance of its coal deposits, in North Atlantic strategy and military operations from the Anglo-French wars in the eighteenth century to the end of the Cold War in the 1990s.

More than two centuries of activity in and around Sydney harbour came to a head during the world wars, when Sydney became a major convoy port in the merchant-ship lifeline that sustained Britain with...