Following Abraham Lincoln's presidential victory in 1861, eleven Southern states withdrew from the Union to form the Confederate States of America, sparking a war between the North and South in which a series of bitterly contested battles and sieges, and countless minor skirmishes, were fought.

DK's The Civil War is divided into seven chronological chapters, each introduced by a general overview of the military and political situation. Each of the war's major engagements is treated individually, while still connecting the complicated relationships between the war's far-flung theaters or the overall strategies of the two sides. The Civil War also includes the reactions of ordinary soldiers and civilians to the momentous events they witnessed, as well as features on major personalities—military and civilian—and on aspects of the war away from the battlefield, such as the effects of the Northern blockade or the fate of prisoners.

The casualty toll of the Civil War still exceeds that of every other American war, before and since, put together. Race and states' rights remain potent issues to this day, making the story of the Civil War as gripping today as it was when it divided the nation more than 150 years ago.