In early 1861 he was given an appointment as the major of the 6th Virginia Infantry Battalion and soon after that he received the colonelcy of the 17th Virginia Infantry. He commanded the 17th at Blackburn's Ford during the First Battle of Manassas, as well during the 1862 Peninsula Campaign. He saw action at the battles of Yorktown, Williamsburg, Seven Pines, and throughout the Seven Days Battles. During the subsequent Northern Virginia Campaign, Corse commanded Kemper's Brigade during the Second Battle of Manassas until he was wounded. He was healthy enough to participate in the Maryland Campaign and was wounded at both South Mountain and Antietam at the head of his regiment. A new brigade was created for him, and he was promoted to brigadier general on November 1. His brigade was placed in a division commanded by General George E. Pickett and was only lightly engaged at Fredericksburg.