Why-has-the-United-States-gone-to-war-since-1898-history-question-help

First one is: Why has the United States gone to war since 1898? Please give one reason and relate it to each war.

Second one is: Was the Cold War inevitable? If so, when did it become inevitable?

Remember, using your own words to write these two essays is important, but you still can search sources online. Moreover, each essay is about one and half-page, and it requires MLA format.