What is the theme in Empire of the Summer Moon: Quanah Parker and the Rise and Fall of the Comanches, the Most Powerful Indian Tribe in American History by S. C. Gwynne?

Major themes addressed in Gwynne's, Empire of the Summer Moon: Quanah Parker and the Rise and Fall of the Comanches, the Most Powerful Indian Tribe in American History, include the ability to adapt, brutality, and the importance of the historical setting.