On October 29, at the Battle of Wauhatchie, Underwood was shot in the thigh and crippled for life. He still was promoted to Brigadier General in November. The wound healed slowly and when he returned to duty in 1865 he was medically unfit for field service, instead doing court-martial duty.[2] In August 1865 he was brevetted to Major General and mustered out of the U.S. Volunteers. Returning to Boston; he served as surveyor of the port and practiced law again. Underwood died there on January 24, 1888.[3]