According to Lincoln's Gettysburg Address,
what principles were at stake in the war?

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:

facts: the 14th amendment

the 14th amendment addresses citizenship rights and equal protection of the laws.

the 14th amendment was intended to protect the rights of former slaves after the american civil war.

the 14th amendment was approved by congress in june of 1866 and ratified by the states on july 9, 1868.

the 14th amendment establishes that all persons born in the united states are citizens and are guaranteed all the rights of citizenship.

the 14th amendment establishes that the law protects all citizens equally.

in this case the passage of the 14th amendment   that was violated was the last part in which it states that there is equal protection of the law.