|Books by Richard Whitten Barnes||
Perhaps the reason tunnels were employed so extensively in that war is due to how static the battle lines remained over the four years of the engagement. Months would pass with little more than several hundred yards changing in their location. Whole battles would be fought for less than a mile of real estate. A small village could be taken then lost the next day.
Between battles there was ample time to fortify defenses, and that meant digging underground facilities for command centers, warehousing materials of war, and billeting men. Tunnels were constructed between these, and on up to the forward positions. The tunnels could extend for miles back to rear positions out of artillery range.
The surprise attack on Vimy Ridge was an excellent example of the Canadians tunneling half way up the hill before storming up the rest of the way on that April 1917 morning.