In the late 1800s, after treaties and reservations failed, the United States Army went to war with American Indians in the West. In your opinion, are there any legitimate reasons for going to war? Check the reasons that you agree with. If you disagree with any of the reasons listed, leave them unchecked. to acquire new territory to try to improve the lives of people in another country to defeat a potential enemy who may be planning an attack to defend against an invading enemy