Foreign Involvement
USA
The US was involved in the Vietnam War because of the domino theory. They gave South Vietnam a lot of military aid. When their troops retreated, the war ended.
France
France was in control of Vietnam a little while before the Vietnam War. The French took over South Vietnam after World War II and the Chinese was in control of North Vietnam. When the Chinese left, France decided to reclaim North Vietnam but the Việt Cộng drove them out.
Japan
Japan occupied Vietnam during World War II. After that war, they left.
China
China was in control of North Vietnam for a while but they left at one point. During the Vietnam War, they assisted North Vietnam, giving them military aid.
Russia
Russia assisted North Vietnam in the war by giving them military aid.