It is a resupply mission. Warships accompanied them because the Confederates had already fired on an unarmed supply ship.
Davis knew what the orders to the ships were. They would not fire if the supply mission proceeded without opposition. firing on it would mean war. He also knew allowing the fort to be resupplied would cause him a political firestorm of outrage. As early as the 8th of April Davis had already decided that he would not allow a resupply of Fort Sumter. Davis had already decided there would be war if Lincoln attempted to resupply the fort.
Lincoln had a Constitutional obligation to defend Federal property and resupply Federal troops. Davis was under not such obligation. Lincoln knew that if he allowed Sumter to surrender without a fight it would also cause a political firestorm of outrage.
If you mean by "confederates", the cadets at the Citadel who had no orders to do so by the Confederate authorities, than yes. But the fact remains, One does not send several armed warships unless you expect to fire cannons from them. Sending warships and calling it a "resupply" mission is deliberately and intentionally deceptive. Lincoln set up his propaganda early. He sends a war mission and calls it a "resupply" and the people in the North who have no idea of the real character of it don't know any better.
Davis had already decided there would be war if Lincoln attempted to resupply the fort.
Funny, virtually all of Lincoln's cabinet had told Lincoln the same thing. Lincoln did it anyway.
It's not really a hard prediction. You send a war force with equipment and troops to a place where the presence of troops was already resented, and yeah, you will very likely start some sh*t.
Lincoln had a Constitutional obligation to defend Federal property and resupply Federal troops.
Again, once the states seceded, real property within their dominion was no longer Federal Property. The state had reassumed it's powers given to the Federal government by the Constitution.
And that's if we just ignore the fact that 75-85% of *ALL* Federal property was paid for by the Southern states.