The Missouri Compromise of 1820, I think.
Adolf Hitler lead the Holocaust so the answer would be the same for both questions. The answer to those is between five and six million Jews died during the Holocaust. It is impossible to know how many Jews died exactly though.
I'm not entirely certain, but I believe the Vietnam conflict was a symptom of the cold because of the still-firm belief that the United States held that <span>communism was threatening to expand throughout South-East Asia. In turn, Russia handed China weaponry as support, who then armed the Northern Vietnamese whom had gone to war with the North Americans. The United States got involved mainly due to that belief, as well as backing South Vietnam, who highly disagreed with the communism of North Vietnam, China and Russia.</span>
The Agricultural Revolution was an important cause of the Industrial Revolution.