Charleston Harbor batteries and ships fired on an unarmed Federal ship bringing supplies and reinforcements months before April 12, 1861, the ship departing undamaged. Lincoln asked the Governor of South Carolina and General Beauregard not to fire on Federal ships or Fort Sumter. It isn’t clear who in the chain of command gave the Charleston Batteries the order to fire on Fort Sumter, but it almost certainly was not Jefferson Davis. A peaceful resolution was possible until that moment.
“Charleston Harbor batteries and ships fired on an unarmed Federal ship . . .”
Grant in his Personal Memoirs, Chapter 4, explains how the Mexican War - and others - start.
“The presence of United State troops on the edge of the disputed territory furthest from the Mexican settlements, was not sufficient to provoke hostilities. We were sent to provoke a fight, but it was essential that Mexico should commence it. It was very doubtful whether Congress would declare war; but if Mexico should attack our troops, the Executive could announce, ‘Whereas, war exists by the acts of, etc.,’ and prosecute the contest with vigor. Once initiated there were but few public men who would have the courage to oppose it . . . Mexico showing no willingness to come to the Nueces to drive the invaders from her soil, it became necessary for the ‘invaders’ to approach to within a convenient distance to be struck.”
Like Grant, Lincoln knew how to start a war. After the Gulf of Tonkin Incident . . . I mean the Fort Sumter Incident . . . war came.