Okay, I'll bite. What letter?
The alleged letter which purports Lincoln informing the commander he would be attacked, to take steps to minimize loss of life, and then surrender the fort.
That is what my friend told me. That was the evidence of his claim that the crises had been engineered by a clever Lincoln. Without such a letter, on what basis could he make the claim that the crises was engineered? The letter as he described it implied a foreknowledge of events.
Why would Lincoln warn the commander unless he expected an attack? That was his argument in claiming that Lincoln cleverly manipulated them into doing it. That Lincoln knew they would.
That letter.