D.) Commonly fought amongst themselves. Before Native Americans came into contact with the Europeans, Native Americans were constantly fighting one another.
In Mesoamerica, the Aztecs engages in aggressive territorial expansion which engulfed surrounding tribes, commonly taking captives for the purpose of human sacrifice. The same is likewise with the Incas who greatly spread their territory through military campaigns in the Andes. This is why it was generally easy for conquistadors such as Cortes and Pizarro to forge alliances with other tribes during the downfall of the Aztecs and Incas.
Plain tribes in the Midwest commonly raided others, for the purpose of access to certain hunting grounds or political purposes. The Iroquois confederacy was formed in Upstate New York because warfare was becoming too destructive for the five tribes who formed the confederacy.
