One man, one decision, and the course of a nation is forever changed. The man is Robert E. Lee. The decision: accept President Abraham Lincoln's April 18, 1861 offer to lead a Union army. Lee assumes command of the Army of the Potomac. He fights its battles on the ground and dates where and when they were actually fought…but herein they are contested in ways found in no history book. In Lee, Lincoln gets the general that eluded him in the opening years of the American Civil War: a highly competent leader, though not an invincible one. Lee soon finds himself plagued by too many subordinates' political ambitions even as he seeks to put others better qualified in command positions. Vainglorious and inept Nathaniel Banks; cocksure former senator and presidential candidate John C. Fremont; grizzled yet lion-hearted Samuel Heintzelman; Thomas Francis Meagher, a convicted seditionist who escapes Tasmania and crosses an ocean to lead the legendary Irish Brigade; and hardened veteran of fighting in the American West John Buford: these are among Lee's generals bad, good, and great. Jefferson Davis's choice to lead his Army of Northern Virginia finds his challenges are much the same. Yet this is not a tale of generals alone. Kind if eccentric Walt Whitman nurses the wounded as he did over a century and a half ago. Stonewall Jackson's talented New Yorker-turned-Confederate mapmaker Jedediah Hotchkiss wields his exceptional skills on the South's behalf. Whitman and Hotchkiss are among the many who bear witness to the remarkable courage and suffering experienced by the men at the sharp edge of combat, men whose families at home come to know the anguish of hunger, disease, and fathers, husbands, and brothers lost. It is a war that could have been but for the decision of a single man.