What were the three lines of trenches?

The three lines of trenches, often referred to in the context of World War I, were defensive fortifications used by opposing armies to protect soldiers from enemy fire. These consisted of the front line trench, where combat and observation took place; the support trench, which housed reinforcements and supplies; and the reserve trench, located further back to provide additional manpower and resources. This system created a layered defense that aimed to reduce casualties and maintain control over the battlefield.