 He was transferred to the Western Theater where, later in 1863, he led his brigade in the attack of Port Hudson, Louisiana.He served as chief-of-staff to Maj. Gen. Nathaniel P. Banks during the Red River Campaign in early 1864, with service at the Battle of Mansfield and Battle of Pleasant Hill in De Soto Parish, Louisiana, Dwight was reassigned to the Eastern Theater and was attached to the 1st Division of the 19th Army Corps.Serving under General Philip H. Sheridan, Dwight later participated in the Valley Campaigns of 1864 and saw action at the battles of Winchester and Fisher's Hill before the end of the war.