Fort Laramie lacked a wall because timber was not abundant and because Plains Indian warriors relied on mobility and fighting on horseback in open terrain rather than siege warfare, leading the army to see permanent walled forts as unnecessary and expensive. The military did build temporary defenses there, and the linear depression at the site is the remains of a rifle trench built in 1865. After Cheyenne and Lakota warriors attacked Mud Springs Station in February 1865, 105 miles east, a detachment of 172 soldiers left to relieve the station and left Fort Laramie dangerously undermanned, prompting orders to build three artillery emplacements linked by rifle trenches. A fortified adobe redoubt built the following year further strengthened the defenses and also served as a corral and teamsters’ quarters, with two hexagonal blockhouses at opposite corners of an eight-foot-high adobe-walled enclosure. After the 1868 treaties, concern about attacks subsided and the defensive trenches quickly fell into disrepair. Evidence indicates the rifle trench had excavated earth piled into a protective berm in front, probably topped with bags of corn for added protection, with a firing step along the front wall and wooden planks lining much if not all of the trench. One soldier considered such works useless for keeping Indians out of the fort and argued that the greater danger came from attacks on small squads caught miles from assistance.