By the spring of 1861, seven Southern states had left the United States. They formed a new country called the Confederate States of America. They said each state had the right to keep slavery. President Abraham Lincoln disagreed. He believed the country must stay together. Fort Sumter sat on a small island in the harbor of Charleston, South Carolina. Union soldiers still held the fort even though South Carolina had left the Union. The Confederate leaders demanded they leave. The soldiers refused. On April 12, at 4:30 in the morning, Confederate cannons opened fire. The bombardment lasted thirty-four hours. Over three thousand shells slammed into the fort's brick walls. The soldiers inside had almost no food left. They could not fire back effectively because they had very little ammunition. On April 13, the Union commander surrendered. Surprisingly, no soldiers on either side were killed during the battle. But the attack changed everything. President Lincoln called for seventy-five thousand volunteers to put down the rebellion. Four more Southern states left the Union in response. The Civil War had begun. It would last four years and cost more than six hundred thousand lives.