During Indochina’s southwest monsoon, which occurs between May and November of each year, the Mekong River becomes engorged with rainwater. Because the Mekong cannot absorb all of the runoff streaming off the jungle-covered highlands of Laos, the plateaus of the Annamese Cordillera, and the rice paddies of east-central Cambodia, the great river is pushed up and over its banks. Unleashed from the confines of its channel, the Mekong spreads its tan waters over thousands of square miles of Cambodia and Vietnam.
In flood, the Mekong’s waters overwhelm the land’s linear, clearly-defined features. Rice paddies, roads, and canals disappear beneath muddy water. In September and October, at the height of the monsoon, the river becomes broad, heavy, and deep. These are the months that Cambodians and Vietnamese living along the lower Mekong lose their hold on the land. People take to houseboats, river galleys, and sampans. Foot and motorized traffic comes to an end. Fishing replaces rice cultivation; and month after month is spent living atop the waves.
One of the regions noticeably affected by the Mekong’s annual flood lies due west of Saigon. In the nineteenth and early twentieth centuries, French colonists referred to the area as the Plaine des Joncs. In the 1950s and 1960s, American military personnel knew the place as the Plain of Reeds. The area is not a plain in the traditional sense, it possesses neither herds of wild ungulates nor expanses of dry-land grasses. Rather, the Plain of Reeds is actually a large seasonal wetland.
Prior to its agricultural development in the late 1970s and 1980s, the plain was an extensive depression in the shape of a rectangle. When the Mekong coursed over its banks, it poured its waters down into the plain, covering the lowland with between one and six feet of water.
The size of the Plain of Reeds fluctuated from year to year, depending on the volume of water draining into it. Early French geographers included portions of Cambodia and Vietnam within its borders. At one time, the plain encompassed 5,903 square miles, with the largest section (4,038 square miles) within South Vietnam.
The plain’s borders extended from just south of the Cambodian river town of Banam east to South Vietnam’s Vam Co Dong River. From there, the marshland stretched southward to the delta community of Tan An. At Tan An, the boundary turned westward and ran in a nearly straight line to the town of Cao Lanh. From Cao Lanh, the Plain of Reeds’ border traced the Mekong River’s left bank, eventually returning to its starting point at Banam.
Since ancient times, the Plain of Reeds acted as a floodway for the Mekong. When the plain filled with water, it lowered the river’s flood crest, ensuring that areas further downstream remained high and dry from floodwaters. The plain acted as a natural reservoir, skimming away some of the Mekong’s high flows and then gradually releasing floodwater back into the main river channel as the flood crest passed on downstream.
Because of the plain’s low elevation in relation to the Mekong, and its frequent inundation, it never held as many settlers as the more arable, less flood-prone regions of the delta to the east and south. In the 1960s, the Plain of Reeds, (like the Rung Sat, the U Minh forest, and the southernmost tip of the Ca Mau Peninsula), was one of the least populated regions in the delta. The delta as a whole averaged 150 people per square kilometer (.62 square miles); but the plain only held twenty-five people per square kilometer.
A combination of factors kept settlers out of the plain. Besides the annual inundation of the region, the soil within the plain contained high levels of sulphates, which impeded rice cultivation. Additionally, the plain’s low-lying, wet soils hindered the construction of stable roadways, which in-turn limited the area’s access to outside markets. The author of a 1969 study noted that even at that late date the area’s dirt roads were of “marginal use.” A handful of navigable canals did exist in the plain, but their number paled in comparison to the number of canals across the central and southern delta.
Villages within the Plain of Reeds consisted of rows of thatch-roofed huts built next to the area’s canals. This same settlement pattern existed across the delta, where the only high, dry land stood adjacent to canals or atop the natural bank lines of streams and rivers.
At least 127 different species of plants grew in the plain. The most prevalent plants included low trees, native grasses, and reeds (which grew as high as twelve feet).
Because of its inaccessibility, low human population density, and vegetation, the plain possessed a large variety of animals, especially migratory birds and amphibians.
The swampy remoteness of the Plain of Reeds had long made it a haven for bandits and insurgents. When the French first seized Cochinchina in the 1860s, Vietnamese rebels fled to the plain to escape imprisonment or death at the hands of the French colonists. A century later, the Vietcong and soldiers of the North Vietnamese Army utilized the region as a base area. The Communists infiltrated men and materials into South Vietnam from Cambodia through the swamp. The Vietcong also cached weapons and supplies in its widely-dispersed villages. In the late 1960s, Communist forces used the plain as a base from which to attack the U.S. 9th Infantry Division at Dong Tam and the South Vietnamese provincial government headquarters at My Tho.
To the Americans, the plain was a marshy region with open expanses of water, blinding sunlight, piss-warm stagnate water, and unfriendly Vietnamese. In 1968, a soldier of the 9th Infantry Division wrote, “…veterans here say that the Plain of Reeds is very similar in climate and terrain to the Everglades in Florida, but there aren’t any alligators to worry about, just leeches, snakes, millions of malaria infested mosquitoes, and of course, the Cong!”
The Americans may have dominated the plain during daylight hours; but at night the Vietcong owned its swampy expanses and darkened villages. Understandably, GIs hated the place: for its heat, its mosquitoes, its lack of a firm, dry footing, and for its hostile peasants.
American grunts entered the plain aboard helicopters, gunboats, and mean-looking hovercraft, but they never stayed long. The Vietcong, on the other hand, never left the place. They were there in 1965 when American combat troops first arrived in South Vietnam and they were still there in 1975 when Saigon fell.