What are support trenches WW1?

During World War I, "support trenches" were found throughout the theaters of the war wherever trench-lines were constructed. Running perpendicular and parallel both to the main defense-line trenches, support trenches enabled front-line troops to communicate with each other, receive supplies, and organize for coming battles without being in the line of fire of the enemy across the (often quite narrow) "no man's land" between enemy lines.