How and when does Harper Lee discuss the Civil War in the novel To Kill a Mockingbird?

At the beginning of Chapter 9, Atticus is having a conversation with Scout about defending an African American named Tom Robinson. Scout goes on to ask Atticus if he will win the case, and Atticus tells her "No, honey" (Lee 48). When she asks why he still plans on defending Tom, Atticus tells her,

"Simply because we were licked a hundred years before we started is no reason for us not to try to win" (Lee 48).

Scout then tells Atticus that he sounds like Cousin Ike Finch. Scout describes Cousin Finch by saying,

"Cousin Ike Finch was Maycomb County’s sole surviving Confederate veteran. He wore a General Hood type beard of which he was inordinately vain. At least once a year Atticus, Jem and I called on him, and I would have to kiss him. It was horrible. Jem and I would listen respectfully to Atticus and Cousin Ike rehash the war. “Tell you, Atticus,” Cousin Ike would say, “the Missouri Compromise was what licked us, but if I had to go through it agin I’d walk every step of the way there an‘ every step back jist like I did before an’ furthermore we’d whip ‘em this time… now in 1864, when Stonewall Jackson came around by—I beg your pardon, young folks. Ol’ Blue Light was in heaven then, God rest his saintly brow…" (Lee 49).

Scout then crawls up on her father's lap, and Atticus tells her,

"It’s different this time...This time we aren’t fighting the Yankees, we’re fighting our friends. But remember this, no matter how bitter things get, they’re still our friends and this is still our home" (Lee 49).

Lee depicts how Maycomb, Alabama still holds the same Civil War prejudice against African Americans. Atticus is essentially fighting an unwinnable battle against Maycomb's prejudiced community. Atticus compares the trial of Tom Robinson to the Civil War and challenges Scout to be tolerant towards their community members despite their conflicting beliefs. He encourages Scout to view their neighbors as friends and treat them respectfully.