Which of the following best states the main reason for the Union's success in the West during the Civil War

no statements but ok.

the statement that best describes the idea of manifest destiny that was used in the 19th century would be that "it was fate that the united states would continue to  expand westward," since people thought the us was "destined" to do so. 

yes.

explanation:

because it let the japanese know who had the upper hand in the war.