Aggression is the intentional act of inflicting hurt on another person. It can be understood in two basic ways: hostility and instrumentalism. Hostile aggression refers to the aggressive behavior of one person towards another for the sole purpose of releasing anger. Other than venting one’s bitter fumes on another, there are no specific ends. Instrumental aggression, however, is the aggressive behavior of one towards another with the purpose of achieving some other ends. The aggression is a means to another specific end. For example, a robber that shoots a banker in order to gain access to the supermarket’s safe represents instrumental aggression. On the other hand, a robber that shoots a banker out of rage for his miserably passing day exemplifies hostile aggression.
To illustrate these two types of aggression, let us recall the war chapters from the Book of Mormon. Throughout the book, two principal groups – Nephites and Lamanites – were continuously at war with each other. The Nephites fought in order to “preserve their lands, and their liberty, and their church” (Alma 43:30), whereas the Lamanites’ purpose in fighting was to “destroy their brethren, or to subject them” and “establish a kingdom unto themselves over all the land” (Alma 40:29). While the Nephites’ purpose in fighting was grounded in instrumental aggression, the Lamanites’ purpose illustrates both hostile and instrumental aggression. In other words, the Lamanites fought against the Nephites sometimes to obtain the Nephites’ lands – instrumental aggression – and at other times simply to express their hatred towards the Nephites for taking away their ‘right’ to “rule over [the] people” (2 Nephi 5:3) – hostile aggression.
At times, Nephite apostate groups (e.g. Amalekites and Amulonites) would incite the Lamanites to anger so that they would fight against the Nephites, not necessarily to obtain the Nephites’ lands, but simply to express their hatred for them (see Alma 24:1). Therefore, the meaning of war and aggression was substantially different for both the Nephites and the Lamanites. While the Nephites always fought with the purpose of defending themselves and their families (instrumental aggression), the Lamanites fought both to obtain Nephite lands (instrumental aggression) and to release their anger upon them (hostile aggression).
http://www.youtube.com/watch?v=TzTZA5AXsdQ 3:42-4:25 (Captain Moroni – Lamanites)