It was to take back their land. This was the war between them and it was called The Indian Wars. It resulted from competition for resources and land ownership as Europeans, Americans and Canadians invaded a territory which had been inhabited by Native Americans.<span> </span>
Answer: I know you said list 3 reasons but here is 4 :)
Explanation: 1 Disease.
2 Guns and Horses.
3 The capture of Atahualpa.
4 Internal Problems.