The Northern army believes that the Civil War is about freeing the slaves. While the Southern army sees it as a cause for state's rights.
"Chamberlain, who is probably the most idealistic character in the novel, believes he is fighting for freedom, the right of every individual to “become what he wished to become,” free from oppression by tradition or the old European-style aristocracies and royalties."
While the South feels that the North is trying to crush their industry, tobacco and cotton so that they would be dependent on the Northern states to survive.
Pride is also a factor on both sides, Chamberlain refuses to retreat when it is obviously the right choice. General Lee refuses, out of pride, to believe that the confederate army is actually losing the war.
Respect is another important theme that affects both North and South. Lt. Gen. Longstreet disagrees with Gen. Lee's strategy, but out of respect he does not question him.
There is a great deal of respect between the Union and Confederate Armies, both had friends on the other side. Many of the soldiers had fought side by side, and vowed to preserve the Union, now the Confederate soldiers felt great guilt by fighting on the side that wanted to break the Union.
Brigadier General Lewis A. Armistead, a Southern leader, is honest and has a strong sense of duty, his good friend, General Hancock is fighting on the side of the North.