Vietnam: the Plan

Evidence of one of history’s legendary naval conflicts lies somewhere beneath the inundated rice paddies of rural Vietnam. In November, Veronica and I had a chance to join an international team searching for the remains of the Bạch Đằng River battle, where seven hundred years ago Đại Việt hero Trần Hưng Đạo defeated the forces of Emperor Kublai Khan. Our team employed advanced remote sensing equipment that allowed us to look for clues hidden below the fields of rice.

A flower blooming beside a rice field, family shrines in the background. © 2011 Douglas Inglis

In the 1950s, public works near the Bạch Đằng River uncovered an array of massive, buried stakes – trees that had been shaped and sharpened into points and set into the ground. C-14 dating revealed they were seven hundred years old, and part of a cunning trap that decimated Mongol power in Southeast Asia.

Vietnamese archaeologists investigate a stake yard. Reblogged from the INA Bach Dang blog.

In 1288, Đại Việt was at war with China, then under the rule of the great Mongol Emperor Kublai Khan. Although it seemed inconceivable, the indomitable forces of the Khan were about to suffer a decisive loss. The wide and powerful Bạch Đằng was a critical conduit for the Mongolian military. However, for over 400 Chinese ships and tens of thousands of troops it became a death trap. The legendary Đại Việt general Trần Hưng Đạo drew the Mongolian fleet into the shallows along the shore of the Bạch Đằng. Lurking beneath the water were thousands of sharpened wooden spikes. When the tide dropped, the Mongols were trapped. The Đại Việt forces fell upon them with fire ships and archers, laying waste to Chinese power.

In the last seven hundred years the Bạch Đằng has shifted coarse and silted in. The battlefield has become rice paddies. To this day famers find massive wooden spikes, remains of the battle, when they dig ponds and canals. Wrecks of Chinese vessels must lie somewhere beneath the fields, amongst the expansive stake beds – but where?

Randy, John, Jun, JB, and Dave, making a plan. - © 2011 Douglas Inglis

Our team is faced with a major problem. The Đại Việt forces concealed tens of thousands of stakes up and down the Bạch Đằng river, but the battle occurred only in a limited area. We cannot dig up kilometers of paddies searching for it. Instead of excavating, team leaders Randall Sasaki and Jun Kimura decided to use advanced remote sensing equipment to look beneath the ground.

Their plan included using Gradiometer Survey throughout both wet and dry rice paddies, Ground Penetrating Radar on the driest fields, and Sidescan Sonar in the canals and waterways. To make sense of the ancient topography, a geologic team drove dozens of cores through the research area.

Gradiometer Survey

JB Pelletier and Doug Inglis, running the gradiometer. © 2011 Veronica Morriss

Magnetometers measure differences in the Earth’s magnetic fields. These variations can be caused by buried iron material such as ship’s fasteners or armor, or by heated material such as brick, burned rock or ceramics. A gradiometer uses dual sensors to measure gradients in these magnetic fields, providing higher resolution data of smaller magnetic features.

JB Pelletier and Veronica Morriss planning a Gradiometer survey. - © 2011 Douglas Inglis

The pair of cesium sensors are mounted on the end of a large counterbalanced boom. An archaeologist carries this rod along with a GPS transceiver, computer data pack and heavy batteries. The entire rig was mounted on a frame pack un-affectionately known to the crew as “The Rack of Pain.” Under the guidance of remote sensing professional J.B. Pelletier, Veronica and I trudged up and down through the rice fields every day, all day, listening to the audible signal of the device. It sounded like the humming of a deranged robot, and terrified the local children which came to investigate.

Ground Penetrating Radar (GPR)

A local woman watches Dave run the GPR. - © 2011 Douglas Inglis

Ground Penetrating Radar (GPR) transmits high-frequency electromagnetic pulses into the ground and records variation in the reflected signals. An archaeologist drags the GPR over the ground to map changes in the density of soil and features beneath the surface. Bringing a GPR along was a gamble – we knew it might not be effective in the rice paddies, but wanted to test it out. Hopefully, we could use it to identify buried stakes, if not shipwrecks.

Iron leaching and mineral deposits in the soil limited its usefulness, disrupting and attenuating the radar signal. We couldn’t see very far or clearly. Because we had the GPR, and it wasn’t being very useful on land, Jun and Randy decided to try it in a boat. Amazingly, this unconventional method worked, and we were able to image the bottom of the numerous ponds and waterways that traverse the landscape.


The team, examining a sample from the core. - © 2011 Douglas Inglis

The topography of our research zone is much different than it was seven hundred years ago. The region was sparsely populated. The small town and communes sit on top ancient islands that once sat in the midst of the river. The rice paddies cover what was once open water or tidal flats. To understand the ancient battle, we had to map and understand the ancient topography. One way to do so was to take geologic samples using a coring device. Experts can look at the sediments pulled up by the coring team and determine where old waterways were, and where there was once dry land. Coring was rigorous work, and the soil was resistant. We bent and twisted several core heads, and broke a number of the extension rods in our struggle.

Each of these methods was fraught with unforeseen difficulties – some laughable and some infuriating. I will post about each of these methods, the complications we faced, how we solved them, and what we found.

Until then, thanks for following!


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Categories: Archaeology, Shipwrecks, Vietnam

Author:Doug Inglis:

I study the archaeology of seaborne exploration and contact. I am passionate about public history and outreach, and write about nautical archaeology at

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