Why did Lincoln break the truce at Fort Pickens and precipitate the war by sending troops to Fort Sumter?
Lincoln did not think that war would result by sending troops to Fort Pickens, and it would give him the appearance of asserting the national authority. Lincoln needed an excuse to start his war of aggression, because Congress did not want war and would not declare war of its own volition. The most-likely hot-spot in which Lincoln could start his war was Charleston Harbor, where shots had already been fired in anger under the Buchanan administration. But the newly-elected governor of South Carolina, Francis Pickens, saw the danger, that Lincoln might, as an excuse, send a force of U.S. Navy warships to Charleston Harbor supposedly to resupply Major Anderson’s Union garrison in Fort Sumter. So Governor Pickens opened negotiations with Major Anderson, and concluded a deal permitting Anderson to send boats safely to the market in Charleston once a week, where Anderson’s men would be allowed to buy whatever victuals they wished. This arrangement remained in effect until a day or so before