Answer:The Civil War brought forth the opportunity of hope for many Native Americans. ... The Indians in some areas hoped this would provide them with the chance to retake some of their lands. Violence broke out among the Native Americans and the settlers and soldiers as they tried to regain the land.
Well they became farmers because there weren't enough crops.
It was known as the Colombian exchange
If you are talking about WW1, then the 3 factors are the Zimmerman Telegram, The sinking of the Lusitania, and economic interests
