Why do you think Lincoln connected his Gettysburg Address to the Declaration of Independence?

In it, he invoked the principles of human equality contained in the Declaration of Independence and connected the sacrifices of the Civil War with the desire for “a new birth of freedom,” as well as the all-important preservation of the Union created in 1776 and its ideal of self-government.

Explanation:

It was an important occasion for the Nation to honor those who had given their lives during the Battle of Gettysburg. ... Lincoln was declaring that the United States would continue to fight to preserve the nation that was created by the Founding Fathers who wrote the Declaration of Independence in 1776.

Explanation:

the indians crossed artificial boundaries, setting the stage for conflict