On June 6, 1944, a massive military force arrived on the beaches of Normandy in a surprise invasion intended to overthrow Nazi Germany. The story of brave Allied forces splashing ashore under heavy fire has been immortalized in novels, memoirs, documentary films, and blockbuster movies — with American GIs cast as the unequivocal heroes of the day.

A famous photo circulating the globe at the time summed things up: a happy GI embraced by ecstatic French girls.

But that photo also illuminates a darker side of the story, according to University of Wisconsin-Madison History Professor Mary Louise Roberts. In her new book, "What Soldiers Do: Sex and the American GI in World War II France," Roberts writes that while heroism abounded during liberation, for some Allied troops, command of geographical territory meant command of sexual territory, as well. As they entered and occupied the port towns of Le Havre, Reims, Cherbourg and Marseilles, many soldiers took what they wanted — when and where they wanted — from the French female population....