In what way is this this effective for both the reader and the youth in chapter 8?

Finally, Henry sees a battle and, at first, participates almost without thinking. He moves from thought to action, and from individual to member of a community:

“He became not a man but a member. He felt that something of which he was a part--a regiment, an army, a cause, or a country--was in crisis. He was welded into a common personality which was dominated by a single desire. For some moments he could not flee no more than a little finger can commit a revolution from a hand.” (31)

Here, Henry becomes part of the army, which subverts individual need for the desire of the group. Merging into a community takes some of the fear and isolation away that each soldier might feel.