According to contemporary estimates, Verdun resulted in 714,321 casualties, 377,231 on the French side and 337,000 on the German one, an average of 70,000 casualties for each of the ten months of the battle.[5] It was the longest and one of the most devastating battles in the First World War and the history of warfare. Modern estimates increase the number of casualties to 976,000.
My response is always the same: read about the Battle of Verdun.