This article focuses on the Chinese laborers in World War I France and their writing activities there. As the story of these laborers has been systematically overlooked in the history of World War I and the subsequent May Fourth Movement, this article endeavors to write the laborers back into the historical narrative that connects China, World War I, and May Fourth. It zooms in on how writing became crucial to the laborers and to the very program under which they were recruited. Between the laborers and a group of volunteers sent by the Young Men’s Christian Association (YMCA), there emerged the first modern Chinese mass literacy program. Writing became, on the one hand, a technology that supported the Allied war effort; on the other, it afforded a medium through which the laborers performed a test run of the new modern Chinese language that ushered in Chinese linguistic and literary modernity. An invaluable piece of writing produced by one of the laborers demonstrates how the “sacred laborers,” not unlike their intellectual counterparts, drove home the critique of the Great War and a particular version of the Chinese Enlightenment. Keywords: World War I, May Fourth, James Yen, Chinese laborers, literacy, YMCA