I believe that this plot was hatched long before April of 1861.

Lincoln was well aware of the distrust of him in the southern states and the statements that certain states (South Carolina) would secede if elected. There was plenty of time, between the election of Lincoln and the South Carolina Secession Ordinance, for Lincoln's cronies to come up with the plan for Maj. Robert Anderson to abandon Fort Moultrie and occupy Sumter.

I believe that Anderson's action was intentional as an act of provocation to get the South Carolina to overreact. The Fly-in-the-ointment was that South Carolina didn't over react and Buchanan wouldn't pursue more aggressive action.

You will note that Col. Robert E. Lee was still loyal to the United States at this time (April 1861). With the departure of a lot of the Southerners in the U.S. Army, such as Beauregard and others, Lee probably was moving up the ladder pretty fast. He was after all offered command of the Union Army before he resigned.

I wonder just how much the "dirty tricks" planning he was aware of? And how much that played into his decision to resign his commission and join the Confederacy. Certainly his loyality to Virginia was admirable. But was that his ONLY reason, as popular history states? I think Lee was a deeper man than to have just loyality to his state as his sole motivation.

After all his family home was Arlington just across the river from Washington DC. He had to have known his home would have been the first occupied if war broke out.