Unfortunately the quickness of WWI was greatly over estimated because of the terrible trench warfare that took place.
Infantry would hunker down in a field. Using only their personal issued spade. And start digging themselves a little hole for cover. Stretch this concept across the front lines. This is called no man’s land. It began the vigorous battles for every inch of land back and forth with miles of death and destruction in between the separate armies. Other than the American Civil War. This type of trench warfare associated with WWI included biological weaponry, such as mustard gas. These types of weapons would later be banned by the victorious committee.