The passage says that "after the war (World War 2) there was a power vacuum." What does this statement mean? How did this power vacuum contribute to the Vietnam War?

Ead the sixth amendment to the constitution. in all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the state and district wherein the crime shall have been committed . . and to be informed of the nature and cause of the accusation; to be confronted with the witnesses against him; to have [the opportunity] for obtaining witnesses in his favor, and to have the assistance of counsel for his defense. what part of the sixth amendment suggests that accused persons will be able to hear the charges against them?