An eye for an eye. Meaning if you committed a crime such as stealing a cow two cows would be taken from you. You get it right?
It lead to that because the U.S. chose to be imperialistic and take over smaller regions with people who didn't have a chance like Hawaii's Quenn Liliuokalani.
The Battle of Gettysburg was a major victory because it eliminated over 65,000 confederate soldiers. It was the bloodiest battle in the civil war.
The Declaration of Independence was made so that the colonies could explain to the foreign nations why they had chosen to separate themselves from Great Britain.
Hope this helps!