The land beneath Ft. Sumter was owned by South Carolina. The U.S. government NEVER purchased this land. The fort, however, was a different story ... it clearly was built and maintained by the U.S. BUT, the disposition of the fort had already been addressed by the two parties in an agreement prior to the Sumter incident.
Sumter is built on a man-made island. Made, I should add, from granite hauled down from New England. There was never any agreement made to turn Sumter over by either Lincoln or Buchanan.
The issue at Ft. Sumter was not ownership, it was breach of contract by the U.S. The C.S.A. & U.S. had reached a peaceful agreement requiring the U.S. to turn over U.S. occupied lands in the sovereign states of the Confederacy. As per the agreement, these posts were NOT to be reinforced by the U.S.
There was no such agreement. All federal property appropriated by the confederates to date had either been abandoned at the time or was turned over by local commanders who were confederate sympathizers.
The commander of the garrison at Ft. Moultrie, MAJ Anderson, under secret orders from Lincoln, left that fort and occupied Ft. Sumter. This was STRICTLY PROHIBITED by the agreement reached between the two countries.
Major Anderson moved his command to Sumter in the last days of December 1860 while Lincoln wasn't inaugurated until March 1861. Lincoln wasn't in a position to issue orders, secret or otherwise, to Major Anderson. Likewise the agreement you spoke of was made by Buchanan and promised that Sumter would not be reinforced if the people of South Carolina did not occupy any government property. The agreement did not forbid shifting of the existing garrison to different positions in Charleston. In any case the agreement became moot when South Carolina violated it by occupying Fort Moultrie and Castle Pinkney as well as the Charleston Armory.
On the 11th of April, 1861, GEN Beauregard demanded the surrender of the fort, as per the agreement. MAJ Anderson at first declined to do so then indicated that he would surrender only if he did not received controlling instructions from Washington City. He knew very well that a fleet of U.S. ships was, at that time, off the coast of South Carolina with men, arms and resupplies waiting out a gale. (N.B.: resupply of Ft. Sumter was STRICTLY PROHIBITED by the agreement between the two countries.)
Again, an agreement that was null and void because of South Carolinian violations of it.
Ft. Sumter was the trigger that Lincoln needed to start the war. It was his Gulf of Tonkin. Conspiring to have South Carolina "fire on the flag" was a perfect scheme for him. War sentiment was already rampant and this infraction, made to look as if the Confederates were at fault, would practically guarantee to fill his call for 70,000 volunteers.
A simple solution to that would have been for the confederate army not to fire. Firing on the fort was suicide and members of Davis' one cabinet told him it was insane to fire on Sumter. But Davis refused to listen. He fired and the south paid the price for his actions over the course of the next four years.
The most cunning treachery was practiced by the U.S. in the negotiations for the evacuation of these various forts, occupied by the U.S. but situated in the sovereign states of the C.S.A., and every principle of honor violated by U.S. government authorities in communications with the commissioners representing South Carolina and the then recently organized Confederate government.
No treachery at all. Davis sent the representatives and Lincoln refused to deal with them. Recognizing them would have been tantamount to recognizing the confederacy as a separate country rather than a rebellious section of the US. Lincoln was not about to give the confederacy a status that it did not deserve.
Referring to the aforementioned agreements regarding the evacuation of the forts in the C.S.A., Horace Greeley, who was certainly not pro-Confederate in his views, stated: "Whether the bombardment and reduction of Fort Sumpter shall or shall not be justified by posterity, it is clear that the Confederacy had no alternative but its dissolution."
But once the confederates started the war, this same Horace Greely coined the phrase, "On to Richmond" as a goal of the war.
I guess he obeys the Ranger's Rules: lie all you want to anyone except another Ranger or an officer...