After Pickett's Charge fails and the Confederates have lost the battle, Tom Chamberlain says to Joshua that slavery is definitely the cause of the war: "Well, then, I don't care how much political fast-talking you hear, that's what it's all about and that's what them fellers died for, and I tell you, Lawrence, I don't understand it at all" (4.6.17).
The fact that the war really was about freeing the slaves is finally totally obvious—if it wasn't before. Even the Confederates admit that their cause is officially a lost one; as Longstreet tells Lee, "You and I, we have no Cause" (4.5.61). At the same time, Chamberlain sees that the Confederates really believed in their fight, and he feels genuine pity as he watches the Confederate soldiers die during Pickett's Charge.
As the conflict ends, Shaara meditates on the corpse-strewn battlefield. The blood soaks into the ground, to grow with the roots of the new vegetation towards heaven. Metaphorically, this blood is reviving the land and bringing America back to life:
The light rain went on falling on the hills above Gettysburg, but it was only the overture to the great storm to come. Out of the black night it came at last, cold and wild and flooded with lightning. The true rain came in a monster wind, and the storm broke in blackness over the hills and the bloody valley; the sky opened along the ridge and the vast water thundered down, drowning the fires, flooding the red creeks, washing the rocks and the grass and the white bones of the dead, cleansing the earth and soaking it thick and rich with water and wet again with clean cold rainwater, driving the blood deep into the earth, to grow again with the roots toward Heaven.
It rained all that night. The next day was Saturday, the Fourth of July. (4.6.27)
Although the book has explored many characters' doubts—even Chamberlain hesitates on questions about race and equality—moral clarity emerges at the end. The Union victory at Gettysburg will cause America to reaffirm its commitment to "life, liberty, and the pursuit of happiness" (though the struggle with racism and segregation would still continue).