During the 1950's, the US had adopted a policy of containment. The goal was to stop the spread of communism on a global scale. This included giving financial and military aid to countries who might fall into the hands of a communist government. A perfect example of this would be South Korea.
During the early 1950's, North Korea (a communist country) invaded South Korea. America, worried about the spread of communism, wanted to ensure that South Korea stayed free of this communist system. To do this, the US helped convince the United Nations to intervene in the conflict between North and South Korea.
Answer:
The reality of war was in stark contrast to the previous beliefs and attitudes Europeans had.
Explanation:
Pre-war Europe included many nations that celebrated their military. To fight was to be honorable and glorious. However, in the Great War, warfare was much more gruesome than previously. The introduction of gas attacks, trench warfare, and other technological/military "improvements" caused lives to be needlessly lost for little to nothing in advancements. During and after the war, people began to realize that it wasn't worth it and the youth suffered terribly.