Monroe Doctrine, (December 2, 1823), cornerstone of U.S. foreign policy enunciated by Pres. James Monroe in his annual message to Congress. Declaring that the Old World and New World had different systems and must remain distinct spheres, Monroe made four basic points: (1) the United States would not interfere in the internal affairs of or the wars between European powers; (2) the United States recognized and would not interfere with existing colonies and dependencies in the Western Hemisphere; (3) the Western Hemisphere was closed to future colonization; and (4) any attempt by a European power to oppress or control any nation in the Western Hemisphere would be viewed as a hostile act against the United States:
The Treaty of Versailles was very harsh on Germany: it had to make huge reparations to the other countries, and it spend years with a very poor economy because of these reparations. This frustrated people and paved way for extremism (which came in the form of Hitler).