[DiogenesLamp]

If Lincoln hadn't sent ships to attack them, they wouldn't have fired on Sumter. They were prepared to give Major Anderson as much time as he needed and he was about to evacuate. Then those ships showed up and the Confederates had already received word as to their orders from their spies and sympathizers in the Navy.

They already knew why those ships were there, and what they represented. They represented a forthcoming attack, according to the orders which had been sent to the Confederates.

Had there been no ships with attack orders, there would have been no attack against Sumter.

[BroJoeK]

DiogenesLamp: "If Lincoln hadn't sent ships to attack them, they wouldn't have fired on Sumter.
They were prepared to give Major Anderson as much time as he needed and he was about to evacuate.
Then those ships showed up and the Confederates had already received word as to their orders from their spies and sympathizers in the Navy."

DiogenesLamp wishes us to focus on the bright-shiny object, Lincoln's "war fleet", while ignoring the real first act of war: Confederates' demand for Fort Sumter's surrender under threat & use of military force.
Lincoln's "war fleet" was only his response to previous Confederate attacks on previous Union resupply efforts, notably the Star of the West.

In short, Confederates were at war against the Union from almost Day One.
Lincoln's "war fleet" was merely a first, tentative, response.