The issue of the divided Union came to a head over the matter of federal forts in the South. When Lincoln took office, only two significant forts in the South were still part of the Union (the rest had been seized by the seceding states). One of these was ___, in Charleston harbor, with fewer than a hundred men. The fort only had enough provisions to last a few weeks, and if no supplies were sent then the fort would have to surrender without firing a shot. But if Lincoln sent reinforcements, the South Carolinians would undoubtedly fight back; they could not tolerate a federal fort blocking the mouth of their most important Atlantic seaport. Lincoln notified SC that an expedition would be sent to provision the garrison, though not to reinforce it. He promised "no effort to throw in men, arms, and ammunition." But to Southern eyes "provision" still spelled "reinforcement." On April 12, 1861, the cannon of the Carolinians opened fire on the fort. After a thirty-four-hour bombardment, which took no lives, the garrison surrendered. The shelling of the fort electrified the North, which at once responded with cries of "Remember Fort ___." The assault on the fort provoked the North to a fighting pitch: the fort was lost, but the Union was saved. B/c the South fired upon the Union, Lincoln issued a call to the states for 75 thousand militiamen (some were turned away however). On April 19 and 27, the president proclaimed a leaky blockade of Southern seaports. The South saw this move as Lincoln waging war against the Confederacy. Virginia, Arkansas, North Carolina and Tennessee, who had all previously voted down secession, reluctantly joined the seceded states.