The president labeled “coercion” of any seceding states as “unconstitutional” in his speech, yet approved of the feverish work to strengthen the federal forts in Charleston Harbor prior to the secession of South Carolina, despite his assurance that there would be no change in the military status of federal installations during the remainder of his administration. By strengthening the forts and refusing to order Major Robert A. Anderson, the federal commander in Charleston, back in to Fort Moultrie, Buchanan broke his pledge. Anderson acted on his won in retiring from Moultrie to Fort Sumter, thereby concentrating his previously strung-out forces in a stronger, more strategic position in the middle of the ship channel. to the South Carolinians, any unauthorized change was an act of coercion. A closer look at Anderson’s movement, though having the appearance and effect of a defensive retreat, shows that it also prevented the Union commander with strong offensive possibilities. With the Union garrison concentrated in a directly unassailable position—for South Carolina had no navy with which to attack a well armed fort—it could train its guns on the city and interdict shipping to this important harbor.
Not only did Buchanan refuse to reoccupy Moultrie, but attempted to covertly reinforce Sumter in an operation disguised as a mercy mission to reprovision a “starving garrison.” when the federal steamship, Star of the West, was driven off by South Carolina shore batteries before it could reach Sumter, Buchanan acted surprised and injured. He tried to lessen the blow by saying that his cabinet had concurred on the decision to reinforce the fort. Jacob Thompson of Mississippi, then secretary of the interior, accused Buchanan of slander, called the movement underhanded, a breach not only of good faith toward South Carolina, but of personal confidence between the president and his advisors, and left the cabinet in disgust.
On December 20, 1860, the same day that Major Anderson evacuated Fort Moultrie, South Carolina acted without hesitation to exercise her rights as a sovereign states and separate herself form the Union. those in the North who had scoffed at South Carolina’s threats to secede were rudely surprised when, on the 9th of January 1861, Mississippi also seceded. Alabama and Florida followed by voting for secession on the 11th day of the same month, joined by Georgia on the 20th, Louisiana on the 26th, and Texas on the 1st of February. In the three months since the election of Lincoln, seven Cotton-Belt states had seceded and begun to seize federal military installations.
There wasn't. Anderson commanded all the forts in the Charleston area and was free to move his men to any of them.
By strengthening the forts and refusing to order Major Robert A. Anderson, the federal commander in Charleston, back in to Fort Moultrie, Buchanan broke his pledge.
No, he did not. The pledge, as recorded by the South Carolina delegation on December 9th, read as follows: "In compliance with our statement to you yesterday, we now express to you our strong convictions that neither the constituted authorities, nor any body of the people of the State of South Carolina, will either attack or molest the United States forts in the harbor of Charleston, previously to the action of the Convention, and we hope and believe not until an offer has been made through an accredited representative, to negotiate for an amicable arrangement of all matters between the State and the federal Government, provided that no reinforcements shall be sent into those forts, and their relative military status shall remain as at present."
Let's deal with the first restriction, no reinforcements. And none were sent to Charleston during the life of the agreement. Your claim is that the U.S. broke the second pledge about the relative military status. It could be argued that Sumter's status as a fort never changed, but that is unnecessary because South Carolina violated their part of the agreement. They promised that nobody would attack or molest any of the forts, yet Anderson's reason for moving to Sumter was due to the very real threat of an attack by the South Carolina mob. This threat was carried in the newspapers and conveyed to him by local leaders such as James Pettigru. Faced with the possibility of attack, Anderson moved. And the imminence of the attack was a violation of South Carolina's promise. So it was they who violated the agreement first, not Anderson.
Not only did Buchanan refuse to reoccupy Moultrie...
South Carolina's seizure of Moultrie after Anderson had left made his return there impossible.
Jacob Thompson of Mississippi, then secretary of the interior, accused Buchanan of slander, called the movement underhanded, a breach not only of good faith toward South Carolina, but of personal confidence between the president and his advisors...
By that time South Carolina had seized Fort Moultrie, Castle Pinkney, the Charleston armory, and were pointing cannon at Sumter. What good faith was due?
On December 20, 1860, the same day that Major Anderson evacuated Fort Moultrie, South Carolina acted without hesitation to exercise her rights as a sovereign states...
Without going into the illegality of that act of secession, I'll just point out that Anderson didn't make his move to Sumter for another 6 days.