It was mainly "a. Genghis Khan" who <span>united and expanded the Mongol Empire, due mostly to his superior military skills, which allowed the Mongols to conquer vast areas of land. </span>
The Mexican-American War, waged between the United States and Mexico from 1846 to 1848, helped to fulfill America's "manifest destiny" to expand its territory across the entire North American continent.
"The Southern states have been conquered and should be punished for their actions." is the correct answer.
