Okay the main difference is "power" is what they can do, "Authority" is was power they already have.
He waited so he could do so on the heels of a successful union military advance. So no more conflict would have to be dissolved.
The encounters between Europeans and the peoples of the Americas and Oceania were really drastic and dramatic for the latter, mainly because Europeans generated the encounters with a mission. Because they were more civilized, they wore clothes and lived in paved cities, Europeans regarded natives as inferior, and consequently they treated them as a lesser culture. The objective of teaching the natives their ways, and their religion to the cultures they regarded as inferior, meant that they hardly considered how natives lived their lives.
