These dugouts protect the local reserves from which supports are supplied and are used for purposes similar to those for which the immediate support dugouts are employed, but on a great deal larger scale. These dugouts are generally near battalion headquarters and from 500 to 1,500 yards behind the firing line. The chief considerations in siting the positions of these dugouts are three: First: facilities for rapid and easy transit to the support and fire-trenches; second: concealment; third: comfort. Comfort should be secondary to the other conditions affecting the siting of the system.