During World War I, J. Gresham Machen worked with the YMCA behind the lines in France. From the conclusion of Letters from the Front: J. Gresham Machen’s Correspondence from World War I, ed. Barry Waugh (2012), we have the following paragraph on the influence World War I had on Machen.
War provides an opportunity for people to do things that they would never choose to do on their own. Though J. Gresham Machen’s service was that of a non-combatant, he was still faced with conditions that required a considerable ability to adapt to dangerous and culturally different situations. In France, Machen worshipped God as he had the opportunity in churches and special services. Surely, he would rather have been home in a Presbyterian
Church, but he made do with services offered by everything from the McCall Mission street preacher to a Roman Catholic chaplain. He was well educated and enjoying the fruit of his academic labors as a professor at Princeton Seminary, but his “Y” work would not at first allow him to use his gifts for the “religious work.” In the States, he enjoyed the privileges of his family estate as he traveled to Seal Harbor, Maine, for his summer vacations, and his finances were sufficient that he could shop at Brooks Brothers and have his suits tailor-made. Machine was always well-dressed in his homeland. In France, he spent months in a wet wool uniform, the odor of which was further enhanced by his own filthy bod that had not been bathed in months. When he began work with the YMCA, his whole world was turned upside down just as were the worlds of the other countless AEF personnel and support organizations. Instead of riding a bicycle through the quaint village of Princeton, he was grabbing rides on ambulances, military trucks, trains, camionettes, and “Fords.” Machen enjoyed sports, but the sport he adapted to in France was trapping and killing rats. Instead of teaching Greek and New Testament studies in the classroom, he created opportunities, with varying degrees of success, to minister the Word of God to the soldiers. It must have been quite a scene to behold Dassy standing over a hot cauldron of chocolate in his matted and filthy uniform, greasy hair, and at times, unshaven beard. In all of this, Machen had adapted to a desperate situation in the hopes that by doing his bit and helping the soldiers in the First World War, the allied victory would deliver Europe from oppression and provide for a lasting peace. (pp. 322, 323)
The Machen Seminar 