3. The Vietnam War: $738 billion
In the height of the Cold War, Americans were in no mood to give up any country to a communist state even if that country was led by unpopular rulers who had killed many of their own people.
Fought from 1965 to 1975, the battle scared millions of Americans and Vietnamese. Yet, it was another war fueled by anti-Communist fervor, in which the United States lost terribly and pulled out of the country just before it was completely destroyed.
The economic cost was high, but it was nothing compared to the toll taken on the Vietnamese people, and the American veterans who returned from an awful conflict to non-existent support.
