What effect did Alfred Thayer Mahan's beliefs have on American foreign
policy?

Mahan was one of the foremost proponents of the “vigorous foreign policy” referred to by Turner. Mahan believed that the U.S. economy would soon be unable to absorb the massive amounts of industrial and commercial goods being produced domestically, and he argued that the United States should seek new markets abroad.

Explanation:

because the vietnam war was fought in an especially brutal and untraditional way

the western roman empire flourished, but the eastern portion of the empire struggled.