All the officers and men on the Harriet Lane knew the Nashville. She was seen weekly on the New York to Charleston run.
The federal ship was interfering with civilian commerce by the use of firepower.
After Buchanan’s illegal use of clandestine military chicanery on the Star of the West, Charleston authorities did not know what to expect of the federal people. Any unknown shipping would be challenged.
The Nashville was no threat to anyone. The Harriet Lane wanted to force a show of colors loyal to the Union, a gigantic metaphor for the reason the Union navy was there in the first place.
Charleston had defended herself in 1776 and would do again in 1861.
Certainly not as big a threat as a lost schooner full of ice cubes.</sarcasm>