Partitioning Vietnam: Making the Division Permanent

A common myth surrounding the 1954 partition of Vietnam holds that three of the primary negotiators at the Geneva Conference, French Foreign Minister Pierre Mendes-France, Soviet Minister of Foreign Affairs Vyacheslav M. Molotov, and Pham Van Dong, Vice Minister of Foreign Affairs for the Democratic Republic of Vietnam (DRV), decided rather nonchalantly, and at the last moment, to establish the demarcation line at the 17th parallel. Apparently, just hours before the approach of the July 21st deadline for an agreement, Mendes-France proposed a partition line at the 18th parallel. Pham Van Dong countered with the 16th parallel. Molotov, hoping to quickly wrap-up the negotiations, then flippantly proposed the 17th parallel. The French and Vietnamese immediately recognized the reasonableness of Molotov’s compromise proposal and agreed to the 17th parallel.

Not only is the above interpretation of events untrue, it ignores how serious the United States, France and the DRV viewed the issue of the demarcation line. Locating the border between the Communist zone of occupation and the French zone became the key stumbling block to an agreement at Geneva. Both French and Vietminh negotiators understood that the location of the dividing line had significant political, economic and military implications.

The United States, which secretly participated in the Geneva talks, initially rejected the idea of partitioning Vietnam. Before the start of the formal conference proceedings in late April, Secretary of State John Foster Dulles noted, “Division of Indochina impractical…Mixed…government would be beginning of disaster….”[1]

In addition to Dulles, President Dwight D. Eisenhower and the U.S. Joint Chiefs of Staff believed any partition of Vietnam would lead to the eventual Vietminh conquest of all of Indochina. Adhering to the assumptions underlying the Domino Theory, which theorized that the loss of one area to Communism would lead to the loss of adjacent areas, the Americans believed that the Communists would use their newly-acquired base area in Tonkin and possibly Annam (northern and central Vietnam respectively) to jump-off to Cochinchina (southern Vietnam), Laos, Cambodia, Thailand, and eventually Malaya and Burma.

Officials in the Eisenhower administration also predicted that French territorial concessions to the Vietminh would undermine the U.S. policy of containment. The U.S. had backed the French in their war against the Vietminh to prevent the spread of Soviet and Chinese influence into Indochina. If the Vietminh acquired all of Tonkin and a portion of Annam at the negotiating table, the U.S. would have failed to keep the Communists restricted to China proper. And officials believed that such an obvious failure of the containment policy would encourage further Communist aggression across Southeast Asia.

On March 12, 1954, Chairman of the Joint Chiefs Arthur Radford wrote Secretary of Defense Charles E. Wilson and warned him of the consequences for the U.S.’s containment policy if the Communists became entrenched in northern Vietnam, “A partitioning involving Vietnam and Laos…as has been suggested…would cede to Communist control approximately half of Indochina, its people and its resources, for exploitation in the interests of further Communist aggression; specifically, it would extend the Communist dominated area to the borders of Thailand, thereby enhancing the opportunities for Communist infiltration and eventual subversion of that country. Any cession of Indochinese territory to the Communists would constitute a retrogressive step in the Containment Policy….”[2] From the American perspective, a partition of Vietnam threatened to unravel the entire U.S dominated global order, which rested on the containment of Communism.

Yet, as the spring of 1954 turned to summer, and the French military situation in Vietnam deteriorated still further, Eisenhower and Dulles reconsidered their stance on partition. Their change in attitude resulted from the realization that without a quick settlement of the war, the Vietminh might overrun the Red River Delta, forcing a humiliating retreat of the French from Tonkin. Without the Red River Delta as a bargaining chip, the French would be hard-pressed to demand any concessions from the Vietminh at Geneva.

By June 1954, the Vietminh were making gains in Annam and Cochinchina. At this point, U.S. officials recognized that if the Vietminh could not be stopped through a cease-fire and subsequent partition of the country, they might seize most of Vietnam, leaving the French holding a handful of coastal enclaves.

Increasingly, the Americans saw negotiations and partition as a means of preserving a viable French presence in at least a portion of southern Vietnam. Eisenhower and Dulles eventually agreed to partition with one major caveat – the demarcation line had to provide the Allies with a solid defensive line.

The establishment of a strong defensive line served as the paramount Western goal in the talks over the division of Vietnam. This is why the Eisenhower administration stipulated that any partition of Vietnam must not threaten the territorial integrity of the other nations of Southeast Asia. In other words, the partition line had to provide for an effective defense of not just southern Vietnam, but also Laos and Cambodia. On May 12, 1954, Dulles clarified the administration’s policy toward partition. “The United States is not prepared to give its express or implied approval to any cease-fire, armistice, or other settlement which would have the effect of subverting the existing lawful governments of the three aforementioned states or of permanently impairing their territorial integrity or placing in jeopardy the forces of the French Union….”[3] Essentially, Dulles let it be known that if a partition line could be established at a defensible location, the U.S. might agree to it.

The question that then plagued the Americans, French, and Vietminh at Geneva was this: where exactly should the demarcation line be established. Not surprisingly, the French and the Americans wanted the boundary as far north in Vietnam as possible. American officials first proposed to French negotiators a partition line at the 20th parallel, which would have provided the Vietminh with only a fraction of the land area they actually held. Understandably, the Vietminh wanted the dividing line as far south as possible.[4]

The Vietminh first proposed a boundary that extended diagonally across Vietnam from Tuy Hoa on the 13th parallel to Pleiku on the 14th parallel. From Pleiku, the line then extended to the Cambodia border. In proposing this boundary line, the Vietminh were not being unreasonable. By the summer of 1954, the Communists controlled approximately eighty percent of Vietnam’s land area, including most of Tonkin, a long stretch of the coastal plain, segments of the Central Highlands, the Plain of Reeds, and a large chunk of the Mekong Delta. This line accurately reflected the Vietminh’s territorial reach. It also ensured that the long-held Communist bastions in the provinces of Binh Dinh and Quang Ngai fell within the Communist zone.[5]

The Americans and French immediately rejected the initial Vietminh proposal. American military analysts determined that the Tuy Hoa-Pleiku demarcation line would make Cochinchina indefensible. Communist access to the Central Highlands and national routes 1 and 14 would enable the Vietminh to rapidly deploy military forces against Cochinchina. To make matters worse, the Tuy Hoa-Pleiku line would have allowed the Vietminh to launch a conventional attack on Cochinchina across a broad front, making it more difficult for U.S. airpower or naval gunfire to stop such an invasion.

Communist forces stationed in the highlands would also be dangerously close to the plains of Cambodia. Proximity to such favorable terrain would give the Vietminh a number of military advantages. From the Tuy Hoa-Pleiku line, the Vietminh could quickly overrun Cambodia. Then, once that country had fallen under their sway, Vietminh units could pivot to the west to threaten Thailand, America’s staunchest ally in Southeast Asia. The National Security Council worried about this possibility when it wrote in 1952, “Thailand would be difficult to defend against an overt attack from the east by way of the traditional invasion route through Cambodia.”[6]

Occupation of Cambodia by the Vietminh would present the Communists with one other major advantage. Rather than turning west to drive into Thailand, the Vietminh could easily swing to the east and push on toward Saigon and the Mekong Delta.

Following the Allied rejection of the 20th parallel by the Vietminh and the Tuy Hoa-Pleiku line by the Allies, the French proposed a boundary at the 18th parallel. A dividing line here would have kept two-thirds of Vietnam in French hands; and most importantly, it would have discouraged a conventional Vietminh invasion of Cambodia and southern Laos, since Communist forces would have had to first pass through the mountains of the Annamese Cordillera before reaching the lowlands of Laos and Cambodia. But this French proposal went nowhere. Neither the Russians nor Vietnamese Communists took the proposal seriously because it bore no relation to the prevailing military situation. In seeking the 18th parallel as a border, the French tried to acquire far more Vietnamese territory than their forces actually held.

To the annoyance of the French, even the Americans did not accept the 18th parallel as a boundary. Instead, the Americans wanted the demarcation line thirty-five miles further south at Dong Hoi. The reason for the choice of the Dong Hoi line is readily apparent from a topographical map of the surrounding area. At only ten miles wide, the coastal plain at Dong Hoi is narrower than at the 18th parallel. Immediately east of the coastal plain lie the azure waters of the South China Sea. While just west of the coastal plain are the high peaks of the Annamese Cordillera. Thus, the coastal plain at Dong Hoi forms a convenient choke point, one that would have allowed U.S. air and naval forces to concentrate their firepower against an invading Communist army. If Communist forces tried to avoid the choke point by turning west into Laos, the climb up the cordillera would have slowed Vietminh mechanized units to a crawl. Bogged down on the precipitous slopes of the cordillera, American airstrikes would have decimated the exposed Vietminh columns. At Dong Hoi, terrain favored the defense. But like the earlier French proposals, the DRV delegation rejected the Dong Hoi line.

Because the talks concerning the demarcation line took place in secret between the military delegations of the French and Vietminh, and between the French and Americans, and neither side kept verbatim records of the discussions, we do not know the exact course of the deliberations. What we do know is that the Vietminh eventually offered to divide Vietnam at the 16th parallel. But the French rejected that line because it meant the forfeiture of two of Vietnam’s largest cities, Hue and Tourane (Danang), and their pro-French populations; it also entailed the loss of the port of Tourane and the French road link to Laos provided by Route 9.

Another reason for the rejection of the 16th parallel related to Hai Van Pass. Had the French accepted the 16th parallel, Communist forces would have been south of the heights of Hai Van Pass, thus complicating the future defense of the French zone.

In the third week of July 1954, the French (with America’s acquiescence) and the Vietminh agreed on the 17th parallel as the demarcation line. The 17th parallel offered the Americans and French many military advantages. The coastal plain there was only twenty miles wide, making it another choke point. If the DRV launched a future invasion of South Vietnam, which U.S. officials believed would come in the form of a conventional cross-border attack, the narrow coastal plain at the 17th parallel would concentrate Communist units in that choke point, ensuring their vulnerability to U.S. airpower and naval gunfire.

An added advantage of the 17th parallel from the U.S. perspective was that the mountains immediately to the west of the coastal plain made it difficult for any land army to skirt to the west to avoid the choke point. An army could go west, but the mountains of Laos would disperse the Communist troop formations, since no major roads existed there. Troop concentrations would break up because they would be required to trod multiple footpaths to the south. Geographical dispersal of the invading ground troops would diminish their offensive striking power, making the invasion force less likely to succeed in overrunning Allied units. Additionally, if the Communists did an end-run around the demarcation line into Laos, the terrain and lack of hard-surfaced roads there would hinder the movement of armor, towed artillery, and mechanized vehicles, all the necessary tools of modern war. Once reduced to foot traffic by the terrain, a cross-border invasion would be easily defeated by the Allies.

The U.S. also agreed to the 17th parallel line because of the presence of the Ben Hai River. The river’s width and depth formed a natural barrier to an invading army. River crossings by conventional forces are difficult in the best of circumstances. When under air and artillery attack, river crossings pose a particular danger to an invading force. Specifically, if the enemy knocks out the bridges across a river, a conventional army can easily come to a complete standstill on the river’s banks. Once immobilized, that army is likely to be destroyed by airpower and artillery. Since the Americans would possess air superiority in any war in Indochina, a Communist army attempting to cross the Ben Hai River would almost certainly face withering American fire.

The 17th parallel gave the Americans the strong defensive line they considered necessary to forestall the loss of the remainder of Southeast Asia to Communism. The Annamese Cordillera, the narrow coastal plain, and the Ben Hai River would help keep the Communists bottled up in northern Vietnam.[7]

What the difficult deliberations at Geneva over the demarcation line reveal is this: President Eisenhower and Secretary of State Dulles had no intention of abiding by the accords’ stipulation that elections for reunification be held in July 1956.

Had the U.S. intended on keeping to the election schedule and to the near-term reunification of Vietnam, it would have been unnecessary for it to seek a dividing line at the 17th parallel. The U.S. could have agreed to a less-defensible partition line at the 16th parallel or at the Tuy Hoa-Pleiku line. The American insistence on the 17th parallel as the dividing line indicated that the Eisenhower administration had every intention of making the division of Vietnam permanent.


[1] The Senator Gravel Edition, The Pentagon Papers, The Defense Department History of United States Decisionmaking on Vietnam, Volume I, (Boston: Beacon Press, 1971), 460.

[2] Ibid., 449.

[3] Ibid., 507.

[4] Ibid., 142, 143.

[5] Ibid., 146.

[6] Ibid., 377.

[7] Ibid., 602, 603.

[8] Ibid., 605.

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