Abraham Lincoln (/ˈlɪŋkən/; February 12, 1809 – April 15, 1865) was an American statesman and lawyer who served as the 16th president of the United States (1861–1865). He preserved the Union, abolished slavery, strengthened the federal government, and modernized the U.S. economy. Lincoln took executive control of the war and shaped the Union military strategy. He responded to the unprecedented political and military crisis as commander-in-chief by exercising unprecedented authority. Two days after McClellan's return to command, General Robert E. Lee's forces crossed the Potomac River into Maryland, leading to the Battle of Antietam. That battle, a Union victory, was among the bloodiest in American history; it facilitated Lincoln's Emancipation Proclamation in January.