What was the main idea behind Lincoln's speech?

Lincoln advocates the words of the Declaration of Independence; and, Lincoln accentuated the Civil War as not just a fight to preserve the Union, but to bring equality to "all" of its citizens: " ... conceived in liberty, and dedicated to the proposition that all men are created equal."

n about 260 words, beginning with the famous phrase, "Four score and seven years ago," Lincoln honored the Union dead and reminded the listeners of the purpose of the soldier's sacrifice: equality, freedom, and national unity.