During World War I, Britain and France imported workers from their colonies to labor behind the front lines. The single largest group of support labor came not from imperial colonies, however, but from China. Xu Guoqi tells the remarkable story of the 140,000 Chinese men recruited for the Allied war effort.

These laborers, mostly illiterate peasants from north China, came voluntarily and worked in Europe longer than any other group. Xu explores China's reasons for sending its citizens to help the British and French (and, later, the Americans), the backgrounds of the workers,...