Surrender implies the USA ceasing to exist and turning itself over to the CSA. That is ridiculous. Vacating brick pile in the middle of the Cooper River is hardly the USA surrendering.
I think that you are underestimating the significance of the Flag flying above that brick pile. The eyes of the nation were on that flag and both Lincoln and Davis felt the pressure. When northerners saw the physical condition of that very flag, after it was lowered by Major Anderson, when he was forced to surrender that brick pile to the “Confederacy”, they united behind Lincoln. And then four years later, Anderson raised that flag back above Fort Sumter.
Of course they did demand 100% abject surrender: of the United States as it existed in 1860, of all Federal properties within reach of secessionists, of such Border Union states as refused to vote for secession (i.e., Missouri), and of any Constitutional process implying "mutual consent" for secession.
Such demands were rejected by both outgoing President Buchanan and incoming President Lincoln.
Indeed. The lengths these False Causers go to is incredible.
The CSA leadership knew the USA leadership quite well. The CSA knew disHonest Abe was a radical and what his agenda was and leaving Sumter in the hands of the yankees would have effectively closed off the port.
The bottom line is, the CSA had just as much claims on federal installations as the north did, even more so since we paid for them.