The Civil war is one of the best-known and most-studied episodes in American history. It resulted in the destruction of the Confederate States of America and the freeing of four million enslaved people. It also established the foundation for the nation’s future economic and political power. Nevertheless, it remains subject to intense debate. The most widely accepted explanation of its causes is that the Civil war was fought over slavery, with its expansion as the trigger for the war. However, recent research suggests that the Civil war was more complex than this narrative would suggest.
The continuous westward expansion of the United States, the rise of abolitionism, and the occurrence of slave rebellions triggered a heated debate over slavery. The antislavery Republican party won the 1860 presidential election and soon after seven southern states (South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, and Texas) seceded from the Union, forming the Confederate States of America.
Both sides mobilized on a scale unprecedented in American history. The Union gathered about 2.1 million military-age men, or more than half its 1860 population. The Confederacy mustered between 800,000 and 900,000 men.
The Union Army was a diverse force. About 7.5 percent of the soldiers were immigrants, and more than one in ten was African American. This infusion of new blood shook up the traditional assumptions about the nature of the Union army. It transformed the war into a war for freedom and made it easier to fight.