Comparing three of the major hydroelectric power-producing countries during the war—Canada, the United States, and Germany—this article considers the implications of expanding hydroelectricity for war production and strategy, and how wartime decisions structured the longer-term evolution of large technological systems. Despite different starting points, all three countries pursued similar strategies in attempting to mobilize hydroelectricity for the war effort. The different access to and use of hydro in these states produced a vital economic and ultimately military advantage or disadvantage. The global dimensions of hydroelectric development during the war, moreover, demonstrate that this conflict was a turning point in the history of electrification.
