Shadow Highway – "They Just Keep a-Coming"

It was a low-tech engineering marvel with a lethal purpose. North Vietnam’s (NVN) shadow highway to the south steadily and stealthily delivered men and materiel to the battlefields of South Vietnam (SVN). Its immense success was reflected in admiring nicknames coined by Americans tasked to shut it down. Because of Ambassador Harriman’s illusion of a neutral Laos through which the shadow highway passed, US Saigon Embassy personnel cynically referred to the Ho Chi Minh Trail (the Trail) as the “Averell Harriman Memorial Highway.” A Marine general called it the “Ho Chi Minh Autobahn,” while a Green Beret who had reconnoitered the route said that at times it was “like the Long Island Expressway – at rush hour.”

 

What Washington dubbed the Ho Chi Minh Trail (actually its official name was the Trường Sơn Strategic Supply Route) had ancient origins in the Annamite Mountains and jungles of Southeast Asia along the western border of what became SVN after the defeat of the French colonialists in 1954. It had long been a loosely connected network of primitive paths and trails through the wilderness trod only by aboriginal tribes inhabiting that sparsely populated, inhospitable area. Only in the late ‘40s during the long Vietnamese war for independence against the French did the network take on some semblance of a logistical trail system. The Viet Minh, the communist-nationalist guerrilla army created by Ho Chi Minh, used the system of trails as a clandestine route for moving fighters from the northern area of France’s Indochina colony to the Mekong Delta in the south below Saigon.

 

After ’54, the system fell into disuse, temporarily as it turned out. In ’59 the Communist Party of NVN decided to significantly support the ongoing low-level guerrilla insurgency against the government of SVN, and the Trail again saw military traffic. Because the early Trail involved climbing steep, heavily forested mountains and traversing rough jungle terrain, elephants were initially used to carry the heavy supplies. Eventually the preferred vehicle for transporting larger-caliber weapons, ammo, and foodstuffs became specially reinforced bicycles pushed, not ridden, by porters. Frames were strengthened, handlebars fixed with a long steering stick, and a pole for stabilizing the bike arose from the seat. Fully loaded, the bikes carried several hundred pounds.

 

 

Bike porters on the Ho Chi Minh Trail

 

After ’65 when the war escalated on both sides, the Trail was widened, and heavy duty Chinese army trucks replaced bikes. A truck-relay system was developed with designated individual sections of the Trail responsible for keeping their own fleets on the road. An underground pipeline was laid to provide fuel to the way stations along the Trail. Early on, Pentagon planners calculated that only as few as 20 truckloads of cargo a day, a fraction of the truck traffic on the Trail at any one time, had to get through for the NVN to meet its supply requirements in the south. By then the Trail had become a dual system – roads safe only at night for the trucks, while troops marched off-road by day, often having to cut trail as they went.

 

Throughout the Trail’s active service from ’59 to the fall of Saigon in ’75, North Vietnamese Army (NVA) troops moved along the route with heavy packs weighing as much as 85 lbs that contained food, clothes, and ammo for both the long journey and, ultimately, the SVN battlefields. To reach the Saigon-Mekong Delta region in ’64 by foot took five months.* Even later, after the system was considerably engineered and improved, the full trek still lasted as long as six weeks. To say that NVN’s ‘long march’ was arduous and tested the limits of human endurance would not be an exaggeration.

 

 

On the Trail through the mountains

 

Not all the NVA troops that moved as units were destined for the Mekong theater of operations. The Trail, which paralleled SVN’s border through Laos and Cambodia, had various ‘exits’, much like an American superhighway. The first exit was just below the Demilitarized Zone (DMZ) separating North and South Vietnam for units assigned to the Hue-Phu Bai sector, the area where brother Jeff Sharlet served in ’64. Although trail time was shorter for troops headed for that sector, they still had to climb over a rugged mountain range in northeast Laos to reach their destination.

 

While the Trail was NVN’s conduit for matching US troop levels in the south with NVA combat regiments and battalions, it was maintained by a separate command consisting of tens of thousands of engineering troops, anti-aircraft units, infantry for ground security, and huge numbers of young women volunteers assigned to roadwork – a highly dedicated and efficient combat support force stationed along the myriad byways and alternate routes of the 8000-mile road system.

 

 

The Trail and its ‘exits’

 

For the NVA troops trekking down trail, the terrain, predators, disease, and weather added to the ordeal. The foot trails were stony, rest areas rough-hewn, and the rainforests through which they passed either suffocatingly hot and humid or rain-drenched, perpetually damp, and steamy during monsoon season. Insects and jungle creatures plagued the transiting soldiers. Mosquitos swarmed in clouds; leeches abounded, whether in water crossings or dropping from trees; and poisonous snakes were ever a danger – everyone carried anti-snake venom, which had to be self-administered within three minutes of a bite. Many soldiers died enroute from disease – malaria, typhoid fever, amoebic dysentery, and many other infectious diseases, even plague, were endemic.

 

However, in terms of sheer ferocity and a staggering death toll, nothing along the Trail matched the US Air Force’s bombing and strafing campaign. When ‘Rolling Thunder’ was launched during spring ’65, Washington believed a relentless bombing campaign of NVN would ‘persuade’ the Communist regime to sue for peace or at least cause them to cease and desist stoking the southern insurgency with streams of men and supplies down the Trail. As the fighting intensified and US illusions about NVN’s commitment and steadfastness began to fall away, the strategic objective shifted to shutting down the pipeline feeding the Viet Cong’s (VC) insurgency against the SVN regime. In military-speak, the objective became ‘interdiction’ to prevent cross-border infiltration from NVN via Laos and Cambodia.

 

For this purpose, the hi-tech might of the world’s greatest military power was brought to bear on the Trail. The battle in the air against the enemy became a veritable separate, secret war apart from the ground war in SVN where GIs and Marines were going head to head with the VC and NVA battalions from the DMZ to the Mekong Delta. The air war was concealed from Congress as well as the American public because a large percentage of the thousands of air strikes were against the Trail in nominally neutral Laos and Cambodia.

 

At the outset prop-driven Douglas trainers were deployed to bomb and strafe enemy formations spotted along the shadowy trail. As the flow from the North increased, the air war escalated when Phantom jets armed with rockets and napalm entered the fray. B-52 bombers from Guam, designed for Cold War intercontinental warfare with the Soviets, were added to the order of battle. Carrying enormous bomb loads, the bombers cruised unseen seven miles up from where their deadly cargoes of 750 lb bombs were dropped from map coordinates.

 

 

B-52s over the Trail

 

As part of the Pentagon’s evolving electronic warfare, a device was created for detecting the presence of humans invisible in the impenetrable jungle below from the air. Colloquially known as ‘people sniffers’, the device was slung under a helicopter which reconnoitered suspected Trail areas, picking up the scent of urine. Coordinates would be transmitted, and perhaps the most destructive air weapon of all would be called in – a converted C-130 cargo plane nicknamed ‘Spooky’ because, being slow and flying at low altitude, it operated at night.  Bristling with automatic rapid-fire Gatling-type guns, Spooky would fly over the identified area, sometimes at only 1500’, and literally shower the jungle below with lead at the rate of 15,000 rounds a minute, eerily lighting up the night with red tracers.

 

One might think such overwhelming power would prevail, would have defeated NVN’s effort to sustain the war in the south. On the contrary, through surprising feats of Engineering 101 and often simple, even primitive countermeasures, the Trail remained a busy military thoroughfare as the vital route to the ground war in the south and ultimate victory in ’75. To counter relentless air attacks, the NVA positioned anti-aircraft guns at critical chokepoints on the Trail, ensuring that US bomb runs were not cost-free. Later, batteries of Soviet surface-to air missiles (SAM) were added, greatly increasing Air Force fixed-wing losses. In the course of the separate war over the Trail thousands of NVA trucks were destroyed and heavy casualties sustained, while the US lost 500 planes with their air crews.

 

Air attacks on the Trail were most effective against bridges over the many rivers that had to be crossed. Engineering crews could put pontoon bridges in place relatively quickly, but they too would be knocked out the next day by prowling Phantoms. For this special challenge to Trail traffic, combat engineers came up with a couple of workable, low-tech solutions. The first was a cable bridge, but one without a roadway. Two strong cables would be strung across a river invisible from the air at water level a truck-width apart. When a truck convoy arrived at a crossing, the tires were removed, the rims aligned on the cables, and the trucks driven across, and refitted with tires on the opposite bank.

 

This bridging technique worked well, but was time-consuming, so another equally simple but even more amazing solution found. A pontoon structure called a ‘peek-a-boo’ bridge was rigged out of the inner tubes of truck tires, and powerful pneumatic pumps were hidden on each side of a waterway. When not in use, the bridge would be concealed by deflating the tubes and letting the structure sink and float beneath the water’s surface. Upon arrival of the trucks, the pneumatic pump would inflate the tubes, the bridge would emerge from the depths, and the convoy would pass over it.

 

Road repair from bomb damage, a constant, was essentially a no-tech job. Without the availability of bulldozers, the largely female road crews posted along the Trail filled bomb craters overnight with just picks and shovels. Occasionally, when a stretch of trail was being repeatedly targeted, the engineers would cut an alternate route below the triple canopy jungle, thus hiding it from the air. Often this involved cutting down trees and clearing brush, but when the NVA realized that their hi-tech adversary had airborne means for detecting foliage decay, they changed tactics. Trees and bushes were instead carefully dug up and transplanted elsewhere, an elementary gardening procedure.

 

However, the NVA’s most primitive but effective countermeasure – and a devilishly clever and amusing one too – was its diversionary response to the vaunted airborne people sniffers. Pots of buffalo urine were hung in the trees in areas away from the Trail causing the planes to release their munitions harmlessly on empty stretches of jungle. Still, the relentless air attacks never ceased.

 

After the Communist Tet Offensive of ’68, Creighton Abrams replaced General Westmoreland (Westy) as overall US commander and inherited not only a grinding ground war, but also the shadowy, hotly contested air war over the Trail. The interdiction campaign remained his major preoccupation right up to the final days of active US involvement in the Vietnam War late ’72. Transcripts from Abrams’ regular briefings clearly indicate that in spite of the best efforts of a superpower, interdiction had remained a frustrating and elusive objective. In late ’70, his deputy commander for air operations conceded that the scope and effectiveness of the Trail had increased:

 

          Over the past year we’ve seen a continual increase

          in the road network, the trails, the alternate route

          structure … which gave the enemy many options

          in terms of moving his equipment and supplies ….

 

          [The NVA’s dispersal of their trucks] has been

          accomplished beautifully, they move at night, they

          move at regular predetermined times, they move to

          one place, stay and hide, unload, pick up another

          truck and move on down, hiding in the [jungle]

          canopy, it’s just an extremely difficult problem.**

 

As American involvement in the war was winding down 18 months later in ‘72, it was evident that NVA infiltration had trumped US interdiction. As a frustrated General Abrams exclaimed to his staff: “it’s a more or less continuous thing – you know, they just keep a-coming.”***

 

Years after in post-mortems on the war, a senior North Vietnamese officer conceded that US air attacks, especially Spooky’s saturation strafing, had hurt them badly, while Westy’s deputy stated flatly in an interview that the fact that the  “Ho Chi Minh Trail was never closed” was a major factor in the failure of the US mission in Southeast Asia.****

 

*J Zumwalt, Bare Feet, Iron Will (2010), 232

**L Sorley, ed, Vietnam Chronicles: The Abrams Tapes, 1968-1972 (2004), 495

***Ibid, 818

****Quoted in R McNamara, In Retrospect (1995), 212