As climate change threatens to open the Northwest Passage to ice-free travel, Canada's sovereignty over the Arctic has become more important to the Canadian government, military, and economy - and more contested by other nations. Although Canada's claim to the Arctic archipelago is now firmly entrenched in the minds of most Canadians, less than a century ago, ownership of the Arctic was much less assured. Acts of Occupation pieces together the engrossing story of how the self-serving ambition of explorer Vilhjalmur Stefansson ultimately led Canada to craft and defend a decisive policy on its claims to the Arctic. Drawing on a wealth of previously untapped archival sources, including the private papers of explorers Shackleton, Rasmussen, and Stefansson, historians Janice Cavell and Jeff Noakes show how unfounded paranoia about Danish designs on the north, fueled by Stefansson's deliberate dissembling of his own motives and by the fears of civil servant James Harkin, was the catalyst for Canada's active administrative occupation of the Arctic. A tale of intrigue worthy of the best popular histories, Acts of Occupation throws new light on an under-studied but transformative period in the history of Canadian Arctic policy and provides much-needed historical context for contemporary debates on northern sovereignty.