Maj. Gen. Nathaniel P. Banks, USA
Maj. Gen. Richard Taylor, CSA
Banks had a Corps operating in the area, while the defenders were a mixed bag of local forces.
US losses were about 250, Confederate around 450.
In April 1863, Maj. Gen. Nathaniel P. Banks launched an expedition up Bayou Teche in western Louisiana aimed at Alexandria. On April 9, two divisions crossed Berwick Bay from Brashear City (now Morgan City) to the west side at Berwick.
On the 12th, a third division went up the Atchafalaya River to land around Franklin, in the Confederate rear, intending to either trap the Rebels (if they retreated) or outflank them if they stood and fought at Fort Bisland. Maj. Gen. Richard Taylor sent Col. Tom Green's regiment to the front to scout the Union strength and retard their advance. On the 11th, the Yankees began their advance in earnest, and late the next day they arrived, arrayed for battle, opposite the defenses. An artillery barrage ensued from both sides until dark; the Confederate fire was heavy and accurate, and forced the Union troops to fall back and camped for the night.
About 9:00 am on the 13th, the Union forces again advanced on Fort Bisland. Combat did not begin until after 11:00 am and again continued until dusk. In addition to the fort's determined garrison, the gunboat Diana, now in Confederate hands, shelled the Yankees. U.S. gunboats joined the fray in late afternoon but before they had much effect darkness brought another halt to the fighting. Later that night, Taylor learned that the Yankee division that went up the Atchafalaya and landed in his rear was now in a position to cut off his retreat. Taylor began evacuating supplies, men, and weapons, leaving a small force to retard any enemy movement. The next morning, the Yankees found the fort abandoned. Fort Bisland was the only fortification that could have impeded this Union offensive, and it had fallen; the road was open for the rest of Banks' campaign.