Erastus Barnard Tyler received no formal military training before the war. He attended Granville College, in Ohio, and went on to enter the fur industry before the outbreak of war. When the Civil War began, Tyler helped raise the 7th Ohio Volunteers, and was elected colonel of the regiment over James A. Garfield. The unit first saw combat in West Virginia on the morning of August 28, 1861, when Confederate soldiers under the command of John B. Floyd surprised Tyler and his men and routed them from the field. During the spring of 1862, Tyler was given the command of a brigade within the division of James Shields, and was commissioned a brigadier general on May 14, 1862. He commanded his brigade at Kernstown, as well as several battles during the Valley Campaign, including the First Battle of Winchester. Tyler commanded Union forces during the battle of Port Republic, but he was defeated by Confederate general Thomas “Stonewall” Jackson. In August of 1862, Tyler was given the command of a brigade in the V Corps. He was held in reserve during the battle of Antietam, but commanded troops during the battle of Fredericksburg and Chancellorsville. At the battle of Chancellorsville, Tyler and his men helped stabilize the Union line. After the battle, the regiments under Tyler’s command were mustered out as a result of their enlistments expiring, and Tyler was transferred to command the defenses of Baltimore on June 30, 1863. He was briefly in command of the VIII Corps during this period, and played a critical role during the battle of Monocacy that kept Confederate troops from threatening Washington. At the end of the war, he was given the brevet rank of major general for his services.