In December the unit was assigned to the newly formed XXV Corps and took part in the failed attack on Fort Fisher, North Carolina, from December 7 to December 27, 1864, and the successful Second Battle of Fort Fisher from January 7 to January 15, 1865, where the regiment was involved in the assault and capture of the fort. The 4th then participated in several other engagements in the area, Sugar Loaf Hill on January 19, Sugar Loaf Battery on February 11, the Battle of Wilmington at Fort Anderson from February 18 to February 20, and the capture of Wilmington and action at Northeast Ferry on February 22, 1865.