What was the notion of Manifest Destiny and how did this idea impact the conflicts of the Civil War?

The notion of Manifest Destiny held that the United States was destined to extend its power, spreading its way of life and democracy all over North America. This expansionism brought new territories but there were disagreement on the slavery issue: while abolitionists would, at first, tolerate slavery in existing territories they did not want the new territories to be slave territories; the economy of the South was, however, heavily based in slave work. This disagreement impacted the conflicts of the Civil War.