Between 1942 and 1945 three million Americans passed through Great Britain. Most were young men in their early twenties, away from home for the first time. They left a country pulling out of its worst-ever depression. They came to the heart of a great but waning empire battered by war. The Brits said the Yanks were "oversexed, overpaid, overfed, and over here." GIs claimed that the Limeys were "undersexed, underpaid, underfed, and under Eisenhower.".

Using a wealth of documents from all over America and Britain, as well as numerous interviews with survivors, David Reynolds explores the ride variety of relationships among pushy, homesick GIs, uprooted, overworked British women, and bored Allied soldiers. He reconstructs the unique world of U.S. aircrews commuting between life and death. And he also examines how Churchill's government and the U.S. Army managed this largest-ever encounter between Americans and British.

Of particular interest are their attempts to impose racial segregation on a society with no color bar, and the reaction of black GIs to the freer atmosphere found in wartime Britain.

Reynolds upsets the conventional wisdom. The GIs look less oversexed when the real pattern of sexual behavior in prewar Britain is established. General Marshall's problems in mobilizing an "army of democracy" explain why that army was overpaid and overfed. Rich Relations also contains the first accurate estimate of the number of war brides, together with moving stories of their experiences and those of the illegitimate children of GIs searching for their unknown fathers.

More broadly, Reynolds discusses the Americanization of Britain, and indeed of the United States itself. In his hands, the GIs embody America's adolescence as a superpower and he follows them as America matures after 1945, listening to their reflections on war and peace.