This link has an image of the artillery plan for the Passchendaele campaign. The barrages were timed at 3 minute intervals. Advancing a hundred yards at time.

This link has an image of the artillery plan for the Passchendaele campaign. The barrages were timed at 3 minute intervals. Advancing a hundred yards at time. http://www.gutenberg-e.org/mas01/images/mas06f.html http://www.gutenberg-e.org/mas01/images/mas06f.html