Some tunnel networks stretched thousands of feet and contained several levels and chambers. The layers of clay used to construct the walls and ceiling defied easy demolition or collapse of the tunnel. Viet Cong tunnels were generally either simple, shallow structures used as refuges and fighting positions or large, complex networks used to evade detection of medical, staging, or command areas. III Corps estimated one such tunnel network had been made over the course of up to 20 years and had small, well-camouflaged entrances. The Army’s search and destroy missions in 1966 began uncovering a large network of tunnels near Saigon. These Soldiers were the “tunnel rats”: volunteer specialists who ventured into the labyrinth knowing that every step in the dark could be their last. Aside from helicopter pilots and Long Range Reconnaissance Patrols, few conventional (non-special operations) Soldiers would place themselves so consistently in danger in Vietnam. While ordinary Soldiers occasionally went into the tunnels the Army recognized the need for a select group of experts to solve this unique problem.

Few Soldiers could fit into the tunnels and follow the guerillas into their lairs. Tunnels were particularly useful in the insurgency and a series of tunnel networks provided the Viet Cong with manufacturing, resupply, and planning space within easy striking distance of their targets. At the same time, the unconventional insurgency of the National Liberation Front of South Vietnam (known as the Viet Cong) presented a very real threat to Soldiers throughout the conflict.

The conventional forces of the North Vietnamese Army demanded respect from the U.S. The Army faced two different threats in the Vietnam War, preventing it from focusing on exceptional performance in either conventional or unconventional warfare.

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