Here is some interesting coverage in the Jewish Chronicle (Dec. 9, 1870) of Jewish soldiers on both sides of the Franco-Prussian War of 1870-71.
Here we read about two pages of a ubiquitous Rodelheim siddur discovered in the trenches, which in its British way is called "interesting" rather than "poignant," as I think is meant:
Here is the complete coverage:
See also an earlier post, 'Two Soldiers and a Shema Yisrael.'