re: 98 Years Ago Today: Battle Of Belleau Wood Begins

In times of little action, yes, they did have rotation schedules for putting units in and pulling them back out of the front lines, although these varied by nation. However, when an attack was on, rotation could be difficult or impossible to accomplish. Consider that preparatory artillery barrages could last a week or more in the First World War. How are you going to get men into or out of the front lines when they are under a literal rain of shell?

The front lines during the battles of Verdun, the Somme, Ypres, and Passchendaele have to rate as some of the most unimaginably horrible conditions ever endured by any member of humanity.