Abraham Lincoln, an opponent of slavery, shocked many when he overcame several more prominent contenders to win the Republican Party's nomination for president in 1860. His election that November pushed several Southern states to secede by the time of his inauguration in March 1861, and the Civil War began barely a month later. Contrary to expectations, Lincoln proved to be a shrewd military strategist and a savvy leader during what became the costliest conflict ever fought on American soil. His Emancipation Proclamation, issued in 1863, freed all slaves in the rebellious states and paved the way for slavery's eventual abolition, while his Gettysburg Address later that year stands as one of the most famous and influential pieces of oratory in American history. In April 1865, with the Union on the brink of victory, Abraham Lincoln was shot and killed by the Confederate sympathizer John Wilkes Booth.