Paul Tillich served his country and his Emperor voluntarily as chaplain during the Great War. He experienced some of the worst battles as a chaplain, and suffered himself from the mental effects of destruction caused by the war. Nevertheless, he remained on his post. During those four years, he performed worship and preached the gospel. Some of his sermons were preserved and published as part of his collected work. This article reports on a first, explorative research on the development of the image of God in these sermons. It shows that in the spring of 1917 Tillich preaches a different God from the one that he presented in the first years’ war sermons. Instead of a God who identifies with the fate of the German nation, God appears from then on as the eternal moment in the soul of every human being, the guarantor of our humanity.