Early on in the deployment of US troops to occupy Vietnam, the need for large scale mosquito control became so great that soldiers began improvising insecticide foggers by mounting pesticide sprayers to diesel truck exhaust (Spicknall 1969). The hack turned out to be much more effective, covering nine square miles per day, compared to 50,000 square feet (0.002 square miles) per day using a conventional manually operated fogger (Spicknall 1969).

As the occupation continued, US Army Soldiers were tasked with “rooting out” Viet Cong and People’s Army of Vietnam soldiers, as well as innocents, from tunnels. The specialized forces designated for the work were dubbed “Tunnel Rats” and tear gas was part of their arsenal to “flush” individuals from caves, which they regularly deployed via pyrotechnic grenades and powdered explosives (Faas 1977; Rottman 2006; Hemmings 2019).

B/W image. Open trench at bottom, center. Pipe runs across trench and into the dirt on either side. Person in gas mask crouched below pipe looking up and forward. Leg in pants and lace up boot stretched over trench leaning against right edge. Other leg and boot partially visible on left. Hand holding lit cigarette resting on foot on left.

Figure 3: Tunnel rat in a gas mask, undated (Hemmings 2019)