The event that caused four additional Southern states to secede from the Union was the attack on Fort Sumter. Fort Sumter was a federal fort located in Charleston, South Carolina, and its surrender was demanded by Confederate forces on April 11, 1861. When the fort's commander, Major Robert Anderson, refused to surrender, Confederate troops bombarded and captured the fort on April 12. This event triggered the secession of Virginia, Arkansas, North Carolina, and Tennessee, which had previously been undecided or hesitant about leaving the Union.
