Vietnam’s coastal plain stretches 638 miles in a narrow arch from Vinh (in the former Democratic Republic of Vietnam (North Vietnam)) to Phan Thiet (in the former Republic of Vietnam (South Vietnam)). It is bordered on the east by the blue waters of the South China Sea, or what the Vietnamese refer to as the East Sea, and on the west by the imposing mountains of the Central Highlands. In its narrowest reaches in northern Binh Dinh Province, the coastal plain is less than a mile wide.
The coastal plain possesses a diverse number of environments. In Quang Tri Province, (which sits south of what had once been the DMZ) gleaming white sand dunes lie just inland from the sea. Here, stunted trees and scrub brush grow out of the poor, sandy soil. Near Quang Tri City, hundreds of gray, rain-streaked burial crypts stand atop the undulating dunes, a testament to the ferociousness of the fighting in this area during the years of the American War.
Further south, near Phan Thiet, the land becomes dry and barren. The coastal plain through this section lies in the rain shadow of the Central Highlands, which means the region doesn’t receive the rainfall necessary for rice cultivation. As a result, the people have turned away from the land and toward the sea for their livelihood. In the harbor at Phan Thiet, dozens of anchored fishing vessels signify the chief occupation of the inhabitants. The vessels range in size from large ocean-going trawlers to small round reed boats. The size of the boats suggests the type of water fished by their owners. The round lacquered boats, which resemble the bullboats employed by the Mandan on the Upper Missouri in the nineteenth century, are used in shallow inlets, estuaries, and along the ocean fringe. The bigger trawlers fish the deep waters further offshore.
In central Vietnam, the rice paddy country lies immediately west of the coastal plain. Here the countryside is divided into small plots of rice, with each rice paddy bordered by four low paddy dikes. The cubed rice paddies, with their diked partitions, have made a checkerboard of the landscape. During the Northeast Monsoon, much of the central coastal plain sinks beneath a murky gray-brown mass of floodwater. The primary means of traveling cross-country during the rainy season is atop the narrow footpaths situated atop the paddy dikes or over the elevated roadways linking the hamlets.
In the Mekong Delta, villages stand on the elevated lands next to dredged waterways or atop the high natural bank lines of rivers. Along the coastal plain, villages exist more haphazardly across the landscape. Villages can be found at the mouths of rivers (such as at Hoi An), on the edge of ecologically-rich seaside estuaries, astride ancient mammalian trails, or atop the high, natural banks adjacent to rivers and streams. Unlike in the delta, where the number of suitable village sites is severely restricted by the available elevated land, in the coastal plain village sites are more dispersed across the countryside.
In the 1960s and 1970s, the coastal plain was not as densely populated as the Mekong Delta, but it did have more people than the plateau country of the Central Highlands. In 1970, the average population density in the southernmost districts of Binh Dinh Province stood at 520 people per square mile. Another heavily populated rural district surrounded the imperial city of Hue.
Major urban centers in the coastal plain can be found at Hue, Danang, Qui Nhon, Tuy Hoa, and Nha Trang. These cities serve as market centers for the paddy country on their environs. In the 1960s, Danang was South Vietnam’s second most populous city, second only to Saigon. Prior to the American military build-up in 1965, Danang, Qui Nhon, and Nha Trang represented three of South Vietnam’s busiest ports. After 1965, the U.S. added to the coastal plain’s list of seaports by constructing modern facilities at Cam Ranh Bay and Chu Lai.
During the French colonial era, engineers laid down a railroad the length of the coastal plain, linking Hanoi to Saigon. Colonial Route (RC) 1 paralleled the railroad line. The French also built highways connecting the coastal port cities with the interior. RC 11 linked Nha Trang to Da Lat via Phan Rang, RC 19 connected Qui Nhon to Pleiku, and RC 9 tied Danang with Laos via Hue and Quang Tri City. The French roads into the interior carried the wealth of the Central Highlands and lowland plains to the coast for export to France; a case in point – the coffee grown on French-owned plantations around Pleiku traveled down RC 19 to Qui Nhon. From there, longshoremen packed the coffee on board ocean-going freighters for shipment to the home country or another colonial possession within the French empire. Vietnam’s system of roads and ports clearly indicated France’s exploitative intent. French geographical constructs pulled the wealth from Indochina’s interior to the coast for shipment overseas.
A number of east-flowing rivers, which drain down from the Central Highlands, divide the coastal plain. Several of these rivers experience regular flooding along their lower reaches during the Northeast Monsoon. The Ben Hai, Cua Viet, and Perfume rivers are all known to flood along their low-lying deltas.
The Vietnamese coastal plain is crowded with people, cluttered with hedgerows, paddies, paddy dikes, tree lines, and hamlets, and frequently filled to the brim with monsoonal runoff. During the American War, the Vietcong employed the coastal plain as a weapon of war. Areas controlled and fortified by the guerrillas slowed the movement of U.S. ground troops, blunted the effects of U.S. airstrikes and artillery fire, and served as guerrilla ambush sites. Frederick Downs, who served with the U.S. Army in Quang Ngai Province in 1967, remembered how the landscape within the coastal plain increased the vulnerability of U.S. troops. His unit had been ordered to protect two armored personnel carriers ensnared in the muck of a rice paddy. He remarked, “Being stuck out in the middle of that rice paddy with the hedgerows all around us would be a sure ticket to a killing. The dinks could slip up to within thirty or forty meters to fire an RPG right into one or both of the tracks.” Ultimately, the natural and built environments of the coastal plain enabled the Vietcong to not only inflict a high number of casualties on American units, but also to fight and win a protracted war against the United States.
 Frederick Downs, The Killing Zone: My Life in the Vietnam War, (New York: W.W. Norton & Company, 2007), 62.