In July 1861 he served as chief of staff to Brigadier General Irvin McDowell at the Battle of Bull Run, and in 1862 held a similar position under Don Carlos Buell.
In July 1861 he served as chief of staff to Brigadier General Irvin McDowell at the Battle of Bull Run. On November 15,1861 he was assigned as chief of staff to under Major General Don Carlos Buell.