The Civil War was the most intense, bloodiest, and complex of all American wars. It made heroes of citizen soldiers, forever changed women’s role in society, and freed more than 3 million slaves. It was also a turning point in the history of the United States, which went from being a relatively weak power to becoming one of the world’s dominant nations.
The war started in 1861, after a new political party, the Republican Party, came to power. The party opposed the expansion of slavery and the extension of the Union into the West, which was causing great concern among Southerners. Southern leaders threatened to secede if the Republicans came to power. South Carolina did so in December 1860, and was quickly followed by Virginia, Arkansas, Tennessee, Florida, Mississippi, Alabama, Georgia, and Texas.
Both sides mobilized armies on a scale never before seen. The Union mustered more than 2.1 million men, nearly half its military-age population, while the Confederacy had no more than 800,000 troops. The North also had the advantage of a huge network of railroads and the ability to maintain those lines, while the South did not.
In addition, the North had more expert military leaders, notably General Grant and his staff. The battles began with small skirmishes and marches, but they soon grew to include enormous campaigns and battles from Shiloh in Tennessee to Gettysburg and Antietam in Maryland, and from Second Manassas and Fredericksburg in Virginia to Chickamauga and Atlanta in Georgia.