On the right, we see one of the panels Lorenzo Ghiberti created in the fifteenth century for the Bapistery of San Giovanni in Florence.  It depicts Cain and Abel, the Bible's first account of humanity outside of Eden (Genesis 4:1-16).  In the story, the older brother kills the younger.

Many Old Testament texts return to the idea of violence. Warfare is mentioned in every book except Ruth.

In several publications, I wrestle with what to do with the Old Testament's violent texts.
This Strange and Sacred Scripture
This Strange and Sacred Scripture contains a chapter devoted precisely to the question, Why is the Old Testament so violent?
Kingdom of Heaven
A question that deeply concerns me is, What convinces people to go to war? In "The Necessity of Permanent Criticism: A Postcolonial Critique of Ridley Scott’s Kingdom of Heaven," Journal of Media and Religion 9 (2010): 129-149, I explore how a Hollywood movie works rhetorically to convince people of war's necessity.
 From Fratricide to Forgiveness
From Fratricide to Forgiveness explores Genesis' teaching on the emotion of anger, which can easily lead to violence.
Bodies, Embodiment
A summary of some of my key arguments in From Fratricide to Forgiveness can be found in "Emotion, Embodiment, and Ethics: Engaging Anger in Genesis," pages 146-158 in Bodies, Embodiment and Theology of the Hebrew Bible (eds. Tamar Kamionkowski and Wonil Kim; Library of Hebrew Bible/Old Testament Studies 465; New York: T & T Clark, 2010). 
Tyndale Bulletin
An even shorter summary can be found in "Dissertation Summary: 'From Fratricide to Forgiveness: The Ethics of Anger in Genesis,'" Tyndale Bulletin 61 (2010): 157-159.
 SBL Forum
In "Teaching the Hebrew Bible amid the Current Human Rights Crisis: The Pedagogical Opportunities Presented by Amos 1:3-2:3," The Society of Biblical Literature Forum 4.1 (2006), I explore the fascinating connections between Amos' oracles against the nations and the Geneva Conventions. 
Dictionary of Scripture and Ethics
I authored the entry on "Prisoners of War" in the Dictionary of Scripture and Ethics.

Related Topic:

Biblical Ethics