The American Civil War, also known as the War between the States or simply the Civil War, was a civil war fought from 1861 to 1865 in the United States after several Southern slave states declared their secession and formed the Confederate States of America (the "Confederacy" or the "South"). The states that did not declare secession were known as the "Union" or the "North". The war had its origin in the fractious issue of slavery, especially the extension of slavery into the western territories. Foreign powers did not intervene. After four years of bloody combat that left over a huge swathe of it's dead and destroyed much of the South's infrastructure, the Confederacy collapsed, slavery was abolished, and the difficult Reconstruction process of restoring national unity and guaranteeing rights to the freed slaves began.