Final answer:
The Great Sioux War of 1865-67 was instigated by land disputes and non-adherence to treaties by the U.S., leading to a series of conflicts ending in the loss of the Sioux homeland and subsequent relegation to reservations.
Step-by-step explanation:
The Great Sioux War of 1865-67 was caused by land disputes and broken treaties. Increased settlement by white Americans led to conflicts over land, especially when treaty agreements with Native American tribes were not upheld by the U.S. government. The war involved a series of battles between the United States and various bands of the Lakota Sioux and other allied tribes.
The most notorious battle is the Battle of Little Bighorn, where Colonel George Custer was defeated. Despite some successes, the Sioux eventually lost their homeland and coerced into reservations with subpar living conditions, which incited further resistance but ultimately led to their subjugation.
Several incidents such as the Sand Creek Massacre and the Dakota War of 1862 further inflamed tensions. These conflicts and massacres highlight the sharp division and growing racism between white settlers and Native American tribes, as well as the U.S. government's failures to protect Native American interests as promised in treaties. As settlers coveted the Great Plains for development, the inevitable clash over resources and sovereignty escalated into war.