On Tuesday, April 4, 1863, Union ironclads under the command of Flag Officer Samuel Du Pont steamed into Charlestown Harbor and in an ill-advised maneuver attacked Fort Sumter.
Confederate shore batteries and those at Sumter returned fire, successfully damaging five of the attacking Union warships. The combined Confederate batteries fired over 2200 shells at their attackers, compared to only 154 fired from the ironclads.
That night Du Pont decided that Charlestown could not be taken by naval force alone. Despite light casualties on both sides, the Union attack had been successfully thwarted, with the USS Keokuk sinking the following morning. Despite this defeat, Lincoln ordered Du Pont to hold his position inside the Charlestown Harbor bar; Fort Sumter was too important a Union target to be disregarded.