The American Civil War lasted from 1861 to 1865 and involved the union (North) fighting the confederacy (South). The South seceded from the North due to political and economic issues surrounding states' rights and slavery. The war began when Confederate troops attacked Fort Sumter in South Carolina after Southern states increasingly seceded in response to Lincoln's election. Over four bloody years of fighting, major battles like Gettysburg and Vicksburg turned the tide in favor of the Union, which eventually prevailed in reunifying the states and abolishing slavery, though at a tremendous cost of over 620,000 lives. Reconstruction efforts after the war faced challenges imposing a new society in the defeated South.