USING TERRAIN TO WIN WARS: AN EXAMPLE FROM THE BATTLE OF PEA RIDGE, AMERICAN CIVIL WAR

During the American Civil War the state of Missouri was considered by both Union and Confederate Armies to be key terrain and essential for control over the Missouri/Arkansas front of the war. With the occupation of Missouri, the Confederates would have access to the Missouri river, granting them greater access to the rest of the north. The Battle of Pea Ridge was fought at Elkhorn Mountain, outside of Pea Ridge, Arkansas, during the winter from 6-8 March. Pea Ridge (also known as Big Mountain or Elkhorn Mountain), is the key physiographic feature around which the battle revolved. The Ridge is a crescent-shaped erosional remnant, topped by a thick sandstone layer within the Fayetteville shale surrounded by flat wooded fluvial deposits. Battlefield conditions played a large factor in how commanders moved troops throughout the terrain. The steep slopes and brush ridden landscape offered geographically and geologically- related problems that included high ground that could not be defended and flat terrain that allowed for undetected troop movement. The key high terrain was interpreted by both armies to be optimal defensible ground. The use of this terrain set up both armies to sustain heavy casualties from the use of explosive artillery. This decision lead to a complete breakdown in command and control by the Confederate senior leadership and inaction by junior commanders allowing for Union troops to occupy more defensible terrain. Here we discuss how the terrain affected rates of troop and equipment movement for both armies through the construction of a digital elevation model for the battlefield and terrain analysis of key locations for the battle. Troop movement of the Confederate Army was disadvantaged by the terrain with steep rocky slopes along Elkhorn and Round Top mountains. The deep incised valleys and rocky outcrops extended lines of troops, slowing down troop advancement and thinned Confederate defensive lines. Overall, the Battle at Pea Ridge failed primarily for Confederate forces because of inadequate terrain assessment and improper use of the geology by the leadership during planning. The smaller, more organized, Union army took advantage of these mistakes which provided them with the tactical and strategic advantage to drive the Confederate Army from the field.