In 1862, he was transferred to the field as chief engineer of the Army of the Potomac and, in 1863 during the Siege of Vicksburg, as the chief engineer of the Army of the Tennessee.
He was transferred to the field as chief engineer of the Army of the Potomac and as the chief engineer of the Army of the Tennessee. This was in 1863 during the Siege of Vicksburg. This was in 1862.