The defenders were a group of gunboats from the Confederate States Navy, termed the Mosquito Fleet, under Capt. William F. Lynch, and about 2,000 Confederate soldiers commanded locally by Brig. Gen. Henry A. Wise. The defense was augmented by four forts facing on the water approaches to the island, and two outlying batteries. At the time of the battle, Wise was hospitalized, so leadership fell to his second in command, Col. Henry M. Shaw.
During the first day of the battle, the Federal gunboats and the forts on shore engaged in a gun battle, with occasional contributions from the Mosquito Fleet. Late in the day, Burnside's soldiers went ashore unopposed; they were accompanied by six howitzers manned by sailors. As it was too late to fight, the invaders went into camp for the night. On the second day, February 8, the Union soldiers advanced but were stopped by an artillery battery and accompanying infantry in the center of the island. Although the Confederates thought that their line was safely anchored in impenetrable swamps, they were flanked on both sides and their soldiers were driven back to refuge in the forts. The forts were taken in reverse. With no way for his men to escape, Col. Shaw surrendered to avoid pointless bloodshed.