Yes, it was so secret that Lincoln sent a letter to Governor Pickens explaining exactly what he was going to do.
What was secret was the fact that the “Star of the West” was carrying WEAPONS.
By the way that Yankee ship is sitting at the bottom of Galveston Bay, sent there by the C.S.S. Alabama :) (before her demise by the Union Navy)
Lincoln said in the message and also to the Northern newspapers that he was sending supplies, and that the:
“garrison in Fort Sumter would be supplied with provisions, peaceably, if permitted, forcibly, if necessary.”
What kind of supplies?
One of the “relief supply” ships, the “Baltic”, intended to disembark troops (300 in number) at Fort Sumter to increase the manning of the fort by a multiple of four or five times it original complement.
This is hardly the action of a ship “carrying supplies only”. A fine example of Lincoln's perfidy, as they called it.
“April 1, 1861-Lincoln sent a secret message to Admiral Foote at the Brooklyn Naval Yard to outfit the “Powhatan” for military use. Foote was instructed under no circumstances to notify the Navy Department of this action. When the “Powhatan” sailed to Charlestown it was disguised as a merchant ship flying the flag of Great Britain with the ships name painted out.”
Source: Days of Defiance, Klein.