Canada at War explores the impact of the two world wars on Canada and Canadians by examining conscription, foreign policy, and politics, with William Lyon Mackenzie King, Canada's longest-serving prime minister, acting as the book's central figure. In this collection of essays, J.L. Granatstein brings together research from archives in Canada and abroad, illuminating Canada's political transition from the British to American sphere of influence in the first half of the twentieth century. Granatstein reflects on the most significant issues affecting Canadians during the wars, showing how this period ushered change into the Canadian landscape and transformed Canada into the country that it is today.