The orders were to take everything that they can, and burn and ruin everything that they can't take. The idea was to destroy infrastructure completely so as to weaken the southern population and the southern support for the war. They would burn farms and pillage everything leaving nothing standing.
The Dakota believes the U.S government was focused on the Civil war and would not fight back. They should attack right away. They believed that if they waited, the government would punish all of the Dakota for the young men killing the white settlers at Action.<span />
Hope this helps:
https://www.google.com/url?sa=t&source=web&rct=j&url=http://thehermitage.com/learn/andrew-jackson/general/war-hero/&ved=0ahUKEwiZjt6U0PnTAhXG7iYKHT4gBAsQFggfMAA&usg=AFQjCNG-keoioPWqUOBY6IOeiEJo1AXj0w
Because the U.S supposedly helped other countries
