Okay the main difference is "power" is what they can do, "Authority" is was power they already have.
Hemingway witnessed D-Day I believe
Try looking it up... I did, and it gives no people, only companies.
By issuing the Declaration Of Independence, adopted by the Continental Congress on July 4, 1776, the 13 American colonies severed their political connections to Great Britain. The Declaration summarized the colonists' motivations for seeking Independence.