What is the meaning of these words from lincoln’s gettysburg address?

In that passage of his speech, Lincoln gives an accurate definition of democracy as "government of the people by the people for the people." It affirms that the victory of the Union in the Civil War would contribute to maintaining democracy as the predominant political system in the United States, and that as such, the United States and its people would not allow it to disappear from the face of the earth.

the western roman empire flourished, but the eastern portion of the empire struggled.