Contrary to popular belief (and a now-removed earlier writeup),
trench warfare was not new in
World War I. It had appeared before, most notably during the
Russo-Japanese War. In fact, one of the enormous mysteries of World War I is how so many
militaries and so many people with so much information on how the weapons and tactics worked could get their predictions on what the war would look like so very wrong. Quick example: The
machine gun, which in fact offers a large advantage to the defense because of its ability to allow fewer troops to put out the same
firepower and because of its weight and the weight of its
ammo, was thought instead to offer an advantage to the
attacker. As a result, the tactic of 'charge the line,' it was thought, would in fact increase the amount of firepower that the attacker could bring to bear against the enemy. For some reason, no one made the next step of saying 'but the
defender can have cover, and unlimited ammo, and can now
engage hundreds of targets instead of only a few.'
Why? There are various answers. A lot have to do with nationalism, a 'culture of the offensive' and the evolution of doctrine before the war. This war was one of the first wars fought steeped in ideological nationalism.