At first glance, the Union's plan seemed brilliant: A regiment of miners would burrow beneath a Confederate fort, pack the tunnel with explosives, and blow a hole in the enemy lines. Then a specially trained division of African American infantry would spearhead a powerful assault to exploit the breach created by the explosion. Thus, in one decisive action, the Union would marshal its mastery of technology and resources, as well as demonstrate the superior morale generated by the Army of the Potomac's embrace of emancipation.

At stake was the chance to drive General Robert E. Lee's Army of North Virginia away from the defense of the Confederate capital of Richmond - and end the war.The result was something far different.

The attack was hamstrung by incompetent leadership and political infighting in the Union command. The massive explosion ripped open an immense crater, which became a death trap for troops that tried to pass through it. Thousands of soldiers on both sides lost their lives in savage trench warfare that prefigured the brutal combat of World War I. But the fighting here was intensified by racial hatred, with cries on both sides of "No quarter!"

In a final horror, the battle ended with the massacre of wounded or surrendering black troops by the Rebels - and by some of their white comrades in arms. The great attack ended in bloody failure, and the war would be prolonged for another year.