How did trench warfare prolong WWI into a much lengthier conflict?

No Man's Land was a place both armies would used to patrol, repair or add barbed wire to their front lines. Trench warfare had a massive impact on soldiers as it caused huge amounts of casualties on the battlefield and also caused health problems of the battlefield ... Trenches were infested with rats and lice. Mar 24, 2016

It prolonged the war because once they dug in they would slowly move forward every few days. It also kept them from having more head on conflicts and doing so prolonged the war effort.