Who invented World War 1 trenches?

Answer 1

Trenches had been used for centuries before WWI, beginning with siege warfare. With the early days of military firearms and artillery the defense had an edge over attackers, particularly of they were defending a strong point such as a castle of a fortress or fortified camp. Such a strong point might be earthworks, where dirt is dug out and piled in front of what becomes an entrenchment, providing cover for the defenders. In laying siege to such a place attackers might first dig a trench just out of range of the defenders weapons, all around the enemy position ("circumvallation"). Then they would dig a trench on an angle, where the enemy could not fire into it, toward the enemy lines, and walk through that to begin another "parallel" around the enemy. Eventually they would get close enough under cover to bring up their artillery into prepared emplacements in their trenches to begin battering down the enemy strongpoint, in preparation for the final assault. This was the way the Americans and French proceeded at Yorktown, at the end of the American Revolution. Earlier in that war Americans had dug in on top of Bunker Hill and created an earthwork, more or less square, and held out through the first three attacks of the British, who out of contempt for what they considered an armed rabble refused to take the time to work at the Patriot position by the "regular approaches" of siege warfare. There was an elaborate body of knowledge of "field fortifications" (earthworks, abatis, cheveaux de frise) and siege warfare, all coming under the heading of "military engineering". This is the bulk of the training professional soldiers get at a military academy. To this day graduates of the US Military Academy are awarded degrees in Engineering when they graduate.

The US Civil War, especially in the last nine months in the east, devolved into trench warfare around Richmond and Petersburg. This might have furnished instructive examples to professional European officers before WWI. But they disdained to study the example, considering that the American Civil War amounted to two armed mobs crashing around in the wilderness. They could not have been more wrong.

So, no one "invented" WWI trench systems. All the regular officers were professionals, who had the same type of training and were very familiar with the concepts of siege warfare and field fortifications. The elaborate trench systems that developed were the application of that knowledge to the problems at hand.