Through Huck's eyes and realizations, we see Twain's view of the Civil War as well as war in general.
In The Adventures of Huckleberry Finn, the feuding families (the Grangerford and the Sheperdson families) can show us Twain's disdain for war. When we see that Grangerford family represents the south and the Sheperdson family represents the North, we see the feuding families represent the feuding nation during the Civil War. While both families are considered to be good, upstanding Christian families, we also see that the two families attend Sunday services armed with their guns.
When asked about what started the feud, neither family can preciously explain the root cause. Instead, both families instead hold fast to their hatred of the other and fight because it is what they have been taught to do. Through these actions, Huck questions the sanity behind a war that no one understands, yet supports.
Huck witnesses the death of Buck Grangerford,a boy about his age. This senseless tragedy solidifies Huck's beliefs that war is unnecessary and comes with too high of a cost.