The shock of the First World War defined the twentieth century for John Dos Passos and many others of his generation. After serving in a French volunteer ambulance service and then with the American Army in France, Dos Passos wrote his novel Three Soldiers (1921). The novel follows the intersecting lives of three Americans as they suffer the wars monotonous and dehumanizing military routine and contemplate escape or revolt against its grinding discipline and extraordinary horrors. Three Soldiers demonstrates the guiding principle shared by Dos Passos and other expatriate American writers that a new age called for a new art, one schooled by new ways of seeing afforded by modern technologies. His recognition of the machine age placed Dos Passos at the center of his centurys new artistic developments, and for his literary accomplishments Jean-Paul Sartre hailed him as "the greatest writer of our time."