The organization and employment of the field artillery of both the Union and Confederate armies evolved throughout the first three years of the American Civil War. This book examines six battles - First Bull Run, Malvern Hill, Antietam, Fredericksburg, Chancellorsville, and Gettysburg to ascertain how lessons learned were incorporated by each side to improve their artillery structure. The reliance on mobility, integration of short and long range artillery, and the development of the fire support plan for various battles are also examined in this study. Both sides used lessons learned from each battle to improve various aspects of their artillery structure. An analysis of the six battles reveals that the more stable leadership of the Confederate army allowed Lee to introduce battalion sized artillery organization one year before the Union army. Additionally, the centralized command and control of the Confederate artillery initially compensated for the superior Union quantity and quality of artillery. However, at the Battle of Gettysburg both sides had developed a robust, responsive artillery command structure.