Abraham Lincoln (February 12, 1809 – April 15, 1865) served as the 16th President of the United States from March 1861 until his assassination in April 1865. He successfully led his country through its greatest internal crisis, the American Civil War, preserving the Union and ending slavery.

Lincoln warned the South in his Inaugural Address: "In your hands, my dissatisfied fellow countrymen, and not in mine, is the momentous issue of civil war. The government will not assail you.... You have no oath registered in Heaven to destroy the government, while I shall have the most solemn one to preserve, protect and defend it."

Lincoln thought secession illegal, and was willing to use force to defend Federal law and the Union. When Confederate batteries fired on Fort Sumter and forced its surrender, he called on the states for 75,000 volunteers. Four more slave states joined the Confederacy but four remained within the Union. The Civil War had begun.