This photo shows Fort Douamont after the battle. The Germans captured the fort early in the battle, but the French massed their artillery for a counter-attack and further bombarded the fort. Similar back and forth gains and losses occurred all over the battlefield, which became a killing field for German troops as well as French troops. It is estimated that over 60 million shells were fired into the battlefield – 15 shells for every square foot of ground. Unexploded shells are still commonly found there today. (Wikimedia Commons https://commons.wikimedia.org/wiki/File:Fort_Douaumont_Ende_1916.jpg)