Question: Should there be an intervention by an outside party?
Albeit a civil war between North and South Vietnam, Vietnam War was more of a proxy war under the influence of two superpowers – the U.S. and Soviet Union (also China to a certain extent) with two opposing ideologies – Capitalism and Marxism (Communism).
In any proxy wars, superpowers not only actively support main belligerents but would also be willing to directly involve should they feel that their interests would be highly damaged if their allies lose such wars such as China and the U.S. in Korean War (1950 – 1953) and Soviet Union in Afghanistan (1979). The same could be said to the Vietnam War where in early 1960s the U.S. was afraid that South Vietnam under Diem might not be able to handle the Viet Cong in the South despite the fact that they had sent military advisors to South Vietnam in the very early years of the war, together with financial backing. The Gulf of Tonkin incident served as a legitimate and justified reason for the U.S. to dispatch its troops to Vietnam.
Likewise, China actively backed and supported North Vietnam. Albeit unofficial, there was evidence that Chinese troops were actually present in the North helping them to protect Hanoi against U.S. strikes. Without China and later Soviet Union’s significant support, North Vietnam could not have won the war.
In short, as a typical proxy war, Vietnam War certainly involved some external interventions regardless whether it was direct or indirect, little or significant. It was inevitable.
Question: What could have been the solutions for both North and South Vietnam?
As the U.S. preferred to have a limited war so as to achieve their goal of preventing South Vietnamese domino from falling as well as prevent China from directly involving in the war which would escalate it even further, it is likely that South Vietnam preferred to have a permanent division of Vietnam.
The situation was more complicated in North Vietnam. In fact, there were some internal conflicts among North Vietnamese leadership. For example, the side of Ho Chi Minh and Vo Nguyen Giap siding with Soviet Union at first preferred to build Socialism in North Vietnam first before thinking of liberating South Vietnam while the side of Le Duan and Nguyen Duc Tho siding with China wanted to “liberate” the South right away. Eventually the more aggressive side won and North Vietnam called for its people to liberate South Vietnam.
To conclude, with the Korean war ended in stalemate, China surely did not want North Vietnam to lose (because of North Vietnamese strategic location towards China and their active and significant support for North Vietnam proved that). So the possibility of a united Vietnam under non-communist government was very little. If the U.S. was more decisive and with a right strategy implemented, South Vietnam could have survived. Vietnam would then become another Korea. Although North Vietnam could have been poor and underdeveloped, China would not have let its neighbour ally easily fall as what happens to North Korea right now. So if there was a permanent division, it would have taken a long while before Vietnam could be united again.
Question: Could there be any possibility that makes North Vietnam turn into an anti-communist state without war?
In order to answer this question, it is best to understand the background and origins of both North and South Vietnam.
Back in the early years of 20th Century, Vietnam and Indochina as a whole was a French colony. There were a lot of movements against the French to gain independence for the country. Under this circumstance, Viet Minh was formed in 1941 as an umbrella group for all the parties such as Communists, Trotskists fighting for Vietnam’s independence. Viet Minh then consisted of mostly nationalists although communists were a majority among them. However, in a power struggle in 1945, communists purged and killed many members of rival groups including Ngo Dinh Khoi – a brother of Ngo Dinh Diem who would become the first President of South Vietnam.This made Viet Minh become a purely communist group and created some sort of hatred between these nationalist groups.
In the aftermath of World War II, Ho Chi Minh proclaimed the establishment of a Communist country in Hanoi (known as North Vietnam) in September 2, 1945. In 1949, non-communist Vietnamese nationalists and politicians formed a rival government known as State of Vietnam in Saigon led by former emperor Bao Dai. After 1954 Geneva Accords which led to a temporary division of Vietnam, State of Vietnam became known as Republic of Vietnam or South Vietnam.
Keeping the background and origins of both North and South Vietnam in mind as well as taking the active support of communist China, who borders North Vietnam just right in the north, for the North Vietnamese communists into consideration, it could be said that there was little if not no possibility that North Vietnam could have turned to a non-communist country. The form of a communist country right below China and North Vietnamese leadership’s desire to unite the country would later cause the Vietnam War.