The document provides a historical overview of several major 20th century conflicts and their connections. It discusses World War II, the rise of the Cold War between the US and Soviet Union, the Berlin Wall, the Korean War, and the Vietnam War. The Cold War was a non-physical war that lasted over 30 years as the two superpowers threatened each other over the containment of communism. Many lives were lost in the wars in Korea and Vietnam due to the overarching fear of communism spreading.