Ideas For Discussion The war between the United States and Mexico was part of a period of American expansion known as Manifest Destiny. Some historians say that the war was a necessary part of the growth of our nation. Other historians say that it was simply an attack on a weaker neighbor and was not necessary for the growth of the United States. Suppose that the war had not taken place. What do you think might have happened to the area that is now Arizona? Would it still be part of the United States? Why or why not? American Progress, by John Gast (circa 1872) Chapter 6 • Review Activities  71