In A Separate Peace, what is the purpose of the similarities and differences between Leper and Brinker?

Leper and Brinker are developed as exact opposites in
personality and behavior. Brinker is the "hub of the class," involved in every activity
and frequently leading them; because of his social skills and ambition, he is the class
politician. Leper, however, has no social skills and lives his school life as a loner
who hides in his own world. Brinker immerses himself in society; Leper loses himself in
nature. Brinker attacks; Leper withdraws. In one essential way, however, Leper and
Brinker are very much alike: They are both terrified of going to war and struggle to
find a way to ease their fear and deal with what is waiting for them in the
world.

By making Brinker and Leper so very different and
then revealing their essential similarity, one that is far more significant than their
differences, the author is making a strong statement about the scope and power of war.
No one can feel secure in the face of it, and there are no strategies to counter its
terror; no one can escape its effects.