نيران صديقة
At the Battle of Gettysburg, Devin's brigade served in Brig. Gen. John Buford's cavalry division that began the battle on July 1, 1863. Devin had become a favorite of Buford's and his rugged leadership style lent him the nickname "Buford's Hard Hitter," while his own men like to refer to him as "Uncle Tommy." As the Confederate attacks began, Devin's brigade was screening the northwest and northern road approaches to Gettysburg, and successfully delayed the arrival of Jubal A. Early's division. Friendly fire from Union artillery on Cemetery Hill caused most of his brigade to withdraw into the town of Gettysburg and they later skirmished with the Confederates as they entered the town. The two brigades of Buford's cavalry division present on the field on July 1 and 2 were withdrawn from the battlefield by Cavalry Corps commander Alfred Pleasonton on the afternoon of July 2.