Louisbourg, France's impressive fortress on Cape Breton Island's foggy Atlantic coast, dominated access to the St. Lawrence and colonial New France for forty years in the mid-eighteenth century. In 1755, Great Britain and France stumbled into the French and Indian War, part of what (to Europe) became the Seven Years' War--only for British forces to suffer successive defeats. In 1758, Britain and France, as well as Indian nations caught in the rivalry, fought for high stakes: the future of colonial America.

Hugh Boscawen describes how Britain's war minister William Pitt launched four...