Bythe Navajo from northwestern New Mexico were raiding the Spanish colonies to steal horses. The Plains Indians constructed a v-shaped funnel, about a mile long, made of fallen trees, rocks, etc.
They were assembled by leaning long poles together and then placing buffalo hides over them.
This painting by Alfred Jacob Miller exaggerates the portrayal of Plains Indians chasing buffalo over a small cliff. Indian armies could only be assembled for brief periods of time as warriors also had to hunt for food for their families. Many lacked the know-how to implement complex irrigation systems.
Plains farmers developed short-season and drought resistant varieties of food plants. This webpage from The West website offers background information on Fletcher and excerpts of a journal kept by her companion, illustrating by example the good intentions behind the misguided Dawes General Allotment Act.
Young men gained both prestige and plunder by fighting as warriors, and this individualistic style of warfare ensured that success in individual combat and capturing trophies of war were highly esteemed  The Plains Indians raided each other, the Spanish colonies, and, increasingly, the encroaching frontier of the Anglos for horses, and other property.
The Outcome of Our Earnest Endeavors Special Agent Alice Fletcher sincerely believed turning native Americans into individual landowners was in everyone's best interests. Peaceful Segregation Ho-Chunk, Mesquakie, and Sauk Indians in the region bounded by the Fox, Wisconsin, Mississippi, and Rock rivers encountered new challenges and opportunities following the War ofwhen accommodation and adaptation eventually gave way to military conflict and removal pressures.