Retired Illinois soil scientist digs up information about Vietnam War tunnels

To satisfy decades of curiosity about the resiliency of the Viet Cong’s underground tunnels, an emeritus soil science professor from the University of Illinois traveled to Cu Chi, Vietnam, to crawl through the restored tunnels. His resulting publication on the wartime tunnels and their soils is attracting significant attention from U.S. veterans groups, military historians, and Vietnam War archivists. “These hundreds of miles of soil tunnels changed the outcome of the Vietnam War. Over time they grew from temporary quarters for a few soldiers to encompass underground villages of soldiers with kitchens, living quarters, and hospitals. Some tunnels even had large theaters and music halls to provide the soldiers with entertainment. “Bombing and search-and-destroy missions from 1966 to 1968 were not able to eliminate these tunnels, and thus the Viet Cong were later able to invade Saigon,” recaps Kenneth Olson, who is retired from the Department of Natural Resources and Environmental Sciences in the College of Agricultural, Consumer and Environmental Sciences at U of I.

Olson is a Vietnam-era veteran who served in the U.S. Army from 1969 to 1973.

“Because the U.S. involvement in the War was winding down, my all-expense-paid trip to Vietnam was cancelled by the Army. I always wanted to go at a later time as a civilian. However, life happened, and I was not able to go for another 43 years,” he says. Specifically, he wanted to examine the Cu Chi and Iron Triangle soil tunnels that connected the Ho Chi Minh Trail in Cambodia and Saigon. He finally took this trip in March 2016 to see restored remnants of these tunnels at Vietnam War Memorial Park in Cu Chi.

“After walking into tunnel chambers and crawling into the tunnel complexes, I utilized my training to assess the well-drained soils and to determine why the tunnels were so difficult to find and destroy by our ground troops and bombers,” he says. Olson’s work is the first to combine historical information about how the tunnels were used during the Vietnam War with information about the soils’ resiliency and their ability to support the tunnels. “During the monsoon season, the Viet Cong were able to dig the tunnels by hand in the moist clayey soil,” Olson explains. “The alluvial terrace soils were degraded in a tropical climate for thousands of years. Iron oxide was slowly dissolved and transported by water draining through the soil to the underlying geological parent materials. During the dry season, the water evaporated and the iron oxide remained in the soil pore space and cemented the tunnel walls. “The soil tunnels became stable, resilient, and hard to destroy with bombs. When aerated and dried, the soil walls took on properties similar to concrete and no additional external support was needed to hold up the ceilings.”

Although exploring and evaluating the tunnels has been his longtime goal, Olson says the resulting article has received even more attention than he expected. The article was published in a Chinese journal and had a record 2250 downloads in the first year. “This paper has taken on a life of its own. The article has now been translated into Vietnamese by three Hanoi scholars. The translated version of the paper is being submitted to a Vietnamese History journal for publication and to the Vietnam War Memorial Park board in Cu Chi for possible distribution to daily visitors and tourists,” says Olson.

“The Vietnam Center and Archive in Lubbock, Texas, has archived the paper. As part of an archived document exchange program, the Vietnam Center is planning to send the Vietnamese translation of the paper to State Records and Archive of Department of Vietnam in Hanoi for their archiving. These papers will then be preserved and made available to future Vietnam War historians.”

The article by Olson and co-author Lois Wright Morton, “Why were the soil tunnels of Cu Chi and Iron Triangle in Vietnam so resilient?” is available from Open Journal of Soil Science. This article was published with funding support from the College of ACES Office of Research and the Iowa Agriculture and Home Economics Experiment Station, College of Agriculture and Life Sciences at Iowa State University.