With regard to your contention:
"And by the way, the North never "declared war" on the South."
I said that the North declared war on the South via blockade.
On April 19, Lincoln issued his proclamation blockading Southern ports. It provided that "a competent force will be posted so as to prevent entrance and exit of vessels" from the ports of the states in rebellion. Then, to make the proclamation official, he signed this document, authorizing "the Secretary of State to affix the Seal of the United States to a Proclamation setting on foot a Blockade of the ports of the States of South Carolina, Georgia, Alabama, Florida, Mississippi, Louisiana, and Texas." The seal was affixed to the blockade proclamation, which was announced that day. It was a de facto declaration of war by the Union against the Confederacy.
http://www.raabcollection.com/manuscript/Abraham-Lincoln-Autograph-7590.aspx
Lincoln was aware that the blockading of ports was an act of war. In fact, since an act of war is, by implication, taken against another state, some in his cabinet argued that a blockade would constitute a tacit recognition of the sovereignty of the Confederacy, something the North wanted to avoid. Lincoln was less interested in the legal definitions than in the military utility of the plan, and he approved it despite the objections.
So, he did three things with this proclamation:
1. He established a state of war on the South,
2. In this effort he formally recognized the Confederacy as an independent entity,
3. He caused the secession of the upper South, thus irreversably bringing on war.
So is bombarding a fort into surrender.