Despite earlier efforts to settle the issue, the slavery question became a major issue in the 1840s and 1850s because the B. Nation Was Expanding West 2. Advocates of Manifest Destiny claimed the motive for territorial expansion was to A) achieve a political balance between North and South B) secure new resources and markets for the United States C) settle the issue of slavery in the West D) extend American liberty to new territories E) ensure that no foreign powers gained territory in North America D. Extend american liberty to new territories