Unseen World War I photos: GermanTrenches

The following photos were taken from 1914-1918 by my great-grandfather Lt. Walter Koessler during his time as a German officer in the first World War. They're part of a collection of over a thousand photos, stereographs and their negatives that my family has been saving for a century. This is an unusually large and complete collection, and I've taken on the task of preserving it and sharing it with you as I believe it deserves.

These photos have never been published before.