Friedrich Siegmund-Schultzes A German patriot and internationalist
Johannes Weissinger ‘German-British peace activities before and during the First World War’ https://www.evangelische-friedensarbeit.de/artikel/2015/weil-der-planet-ein-dorf-geworden-ist
Paul Tillich: At the age of 27 when the war was declared, Tillich volunteered for army service and given his academic and ministerial qualifications was appointed as a military chaplain. He served on the Western front, wholeheartedly committed to his fellow recruits, the German war cause and his Christian faith. His subsequent experience of the brutality and senselessness of the suffering around him led him to reject the version of Christianity  expected of a military chaplain by his regimental general; prayer would not protect a soldier from enemy fire. He does not abandon those he is serving alongside, he continues to hold to his patriotic loyalties, but he looks for a deeper sense of God present within fragilities of human civilisation and the terrors of war on both sides. He was awarded the Iron Cross, but he left military service with a breakdown. Subsequently, he developed a version of religious socialism challenging the theologised nationalist rhetoric of the war. file:///C:/Users/NewUser/Downloads/Helping_Germans_Meet_Their_Maker._WW1_ch.pdf;
http://people.bu.edu/wwildman/tillich/resources/popculture_tillichandsocialism.htm.
Karl Barth: Though working outside Germany, already in 1915, whilst working as a youthful pastor in the Swiss village of Safenwill, Karl Barth (probably the most influential of all 20^th century Protestant theologians) rejected this as a sell-out to the ideology of war. His theological mentors could no longer be trusted – their scholarship had changed ‘into intellectual 42cm cannons’ A Unique Time of God: Karl Barth’s WW1 Sermons (ET 2016). "ninety-three German intellectuals issued a terrible manifesto, identifying themselves before all the world with the war policy of Kaiser Wilhelm II and Chancellor Bethmann-Hollweg. For me it was almost worse than the violation of Belgian neutrality. And to my dismay, amongst the signatories I discovered the names of almost all my German teachers".."It was like the twilight of the gods when I saw the reactions of Harnack, Herrmann, Rade, Eucken and company to the new situation.".."To me they seemed to have been hopelessly compromised by what I regarded as their failure in the face of the ideology of war." Their 'ethical failure' indicated that 'their exegetical and dogmatic presuppositions could not be in order'." Eberhard Busch Karl Barth  His Life from letters and autobiographical texts (1975) p 81.
In subsequent writings he continually addressed the matter of war and peace in Christian experience: https://politicaltheology.com/barth-on-war-peace-and-pacifism-a-primer