The Flu’s Effect on the War

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An excerpt from the Journal of the Association of Military Surgeons of the United States, “Influenza—U.S. Army,” 1920. Courtesy of the University of Toronto Medical Heritage Library via Internet Archive.

Influenza, and the staggering loss of life that resulted, determined the course of the fighting and of international relations during World War I. The American military was one of several armies severely weakened by the flu. All nations involved in the war were hard-hit by the pandemic, with American losses alone numbering over 63,000. More than half of the total losses in the last months of 1918, in fact, were attributed to disease. The British forces, by comparison, lost roughly one in nine servicemen to the flu during a similar period, and the Central Powers suffered comparable losses.

It is difficult to speculate how differently the war might have turned out had the flu not been a factor, but it is undeniable that the arrival of this universally lethal enemy decimated a large portion of military forces, weakened positions, and changed plans worldwide.