This book examines the use of artillery by the Union Army of the Cumberland during the Battle of Chickamauga on 19 and 20 September, 1863. The book methodology is an analysis of the terrain, technology, tactics, organization for combat, and leadership during the battle. This book shows that the Union did not employ artillery effectively due to poor organization for combat and failure of leaders to use the weapons systems in accordance with their strengths. The failure to plan for artillery use on 20 September directly led to weakness on the left flank, which the Confederates exploited. The ensuing havoc led Union leaders to attempt to reorganize their artillery structure while in contact with the enemy, leading to predictable failure. This book shows the failure of artillery, a branch that was nearing the end of its relevance during the American Civil War due to technological change. As military thinkers today go through the process of redesigning the force, they can use the lessons of the artillery at Chickamauga as an example of the wrong way to employ a force at the end of its life cycle.