The confederate forces had been firing at anything flying the U.S. flag long before Lincoln's resupply effort. On at least two prior occasions they had tried to initiate hosilities by firing on unarmed ships. In the end, they came to the conclusion that the only way to get their war was to bombard the fort itself.
Overcharacterization for polemical effect -- how well you do it.
The Southerners were concerned only with the possibility -- the probability (about which they guessed aright) that Lincoln had been lying to them and would attempt to reinforce the garrison with more troops. He did.
In the end, they came to the conclusion that the only way to get their war was to bombard the fort itself.
Oh, I'm sorry, but "getting their war" was Lincoln's purpose -- and will you insist I quote Lincoln's personal secretary, John Nicolay, to you to prove it?
Starting a war was Lincoln's idea. I think he wanted a war all along --ever since 1856, when he finally concluded that there was no constitutional way to abolish slavery. (So, he decided on an unconstitutional one -- a civil war.)