Character Analysis
Buford's cavalry troops are the first soldiers to intercept the Confederate Army. Although the South technically wins the first day of fighting—at least they kill more people—Buford makes sure that the Union holds a position that will be advantageous in the following days. In the process, he witnesses the death of General John Reynolds, a way important Union commander, even if he's not a big presence in The Killer Angels (since, you know, he buys the farm early on).
By holding Lee's troops off for a while, Buford lets the Union Army come in behind him and take the high ground from Culp's Hill and Cemetery Hill in the north down to Little Round Top in the south. By making sure that the Union holds this strategically valuable ground, Buford plays a crucial role in making sure that the next two days of the battle will favor the Northern side.
Buford isn't all that reflective about slavery; he seems to be fighting more because it's his duty, and because he doesn't want to rebel against his own government. But he likes the South from a vacationer's perspective… he's even thought about moving there to retire:
Could you ever travel in the South again? Probably not for a while. But they had great fishing there. Black bass rising in flat black water: ah. Shame to go there again, to foreign ground. Strange sense of enormous loss. Buford did not hate. He was a professional. The only ones who even irritated him were the cavaliers, the high-bred, feathery, courtly ones who spoke like Englishmen and treated a man like dirt. But they were mostly damn fools, not men enough to hate. But it would be a great shame if you could never go south anymore, for the fishing, for the warmth in winter. Thought once of retiring there. If I get that old. (1.3.77)
Buford's perspective highlights the fact that the country really is unified in many ways: North may be fighting South, but North and South have more in common than they have not in common.