From publisher blurb:
TRIBES…
The first portion of this book fills several gaps in the setting information originally presented in the Core Rulebook, namely those associated with the pastoral and tribal populations of the Ancient Near East.
Players who want to create characters who hail from the world beyond the cities’ walls will find a discussion of pastoral existence, new skills, new weapons (like the lasso and the throw stick), and tribal magic items. Additionally, for groups using the optional Feats system, this book includes several feats appropriate to migratory life in the arid world of Mesopotamia.
…and ARMIES
The second half details the organization and equipage of a city-state’s armed forces, and describes rules for adjudicating mass combat situations, along with associated tactics and a method by which player characters may help or harm opposed units.