What is the role of dharma in Mahabharata?

The concept of dharma, or duty, is a large issue in the
Mahabharata.  The characters in the work all face the issue of dharma in one way or
another and their response to it forms both the structure of the work and the lessons
taken from it.  Arjuna has one of these moments when he must face his kinsmen in
battle.  Seeing them line up against him, without any fear, and recognizing that his
dharma is to face and defeat them is a moment of truth for him and provides a similar
moment for the reader.  The issue here is whether it is better for him to capitulate and
shirk away from his dharma of fighting against evil or whether he must face the arduous
and difficult notion of confrontation.  Through Krishna's guidance, it is clear as to
what he must do.  His embrace of dharma, of his duty or responsibility as both a warrior
and a human being, and his faith in Krishna's promises that Arjuna's dharma is part of
something larger is what gives Arjuna the strength to carry out his responsibility.  It
is also a message for us, the reader, to recognize our own "Arjuna moments" and rise to
them, meeting our dharma and embracing it.