Trade, WAR AND MORE
The Sioux people regularly traded with other tribes of Great Plains, especially the Arikara. When trading, they communicated with Plains sign language. They also traded with other Sioux tribes.
The Cheyenne tribes were very close allies of the Sioux.
In war, the Sioux and their opponents usually did not fight for territory but to prove their courage. Instead of trying to kill one another or destroying villages, the warriors would steal each other's weapons and mildly hurt their adversaries. Sometimes they would adopt their captured enemies as their own. When going into war, the Sioux would not attack close to home. They did this so women, children and other men would be safe, away from the battle. They often fought with the Assiniboine, Ojibwe and Kiowa people.