Underground rooms called dugouts were used for a variety of purposes from storing supplies, housing troops and communication centers near the front line. Many were built deep underground using heavy timbers and corrugated iron and were often reinforced with steel rail and concrete in order to withstand heavy artillery bombardments.
The Post of Command (PC) served as the advance headquarters for accompany or a platoon on the frontline. Often place in a dugout with sleeping quarters for company staff, the PC served as a front line office and communications center.
My platoon was in the company support position. Slightly to our rear was a large dugout where our company command post was located. It was connected by telephones to all our platoon command posts and to the battalion command post. At several places along out trench there were narrow tunnels leading downward into the earth to our sleeping places. To enter, one had to stoop and descend into a dark, damp, smelly hole. When enough depth had been reached the tunnel was widened and became level. Short cross tunnels led off of it. One could sleep if he was tired enough. The whole place was infested with rats, body lice and bed bugs. At the far end of the tunnel was a shaft and ladder to escape by in case the entrance was cave in by shellfire. Near the entrance of the dugout,
and in the opposite direction, a spur trench lead to a trench latrine.
Notes from the History of the Fifth Division, A.E.F.