Vietnam War: Forest Fire as a Military Weapon - Paperless Archives

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Example of a Desiccation Plan: Saigon, Republic of Vietnam
Figure 40 shows the monthly temperature, precipitation, and probability of muccesful burning for Saigon. From the
definitionsgiven in the section on Climatic Types, there are only 4 "bum" months, but the yearly (-) value is over 26 and
the yearly ( + ) value is over 100. So Saigon falls in Precipitation Class HULB: Humid-long burn season. The average daily
mean temperature for the coldest 3 months is 79 degrees, and the average daily minimum for the same months is 65 degrees.
So Saigon falls in Temperature Class FF: Frostfree winter.
The vegetation type is dense hardwood forest with relatively continuous ground-story vegetation, but deficient ground
litter and dead stems. The best burning period is in late winter (February 15 - March 15).
The first step in planning desiccation treatment is to look at the average weather situation during the months preceeding
February 15, as follows:
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I. Two months of hot dry weather occur after December 15 - favorable for dying and drying of sprayed vegetation,
with minimum deterioration of leaf fuel on the ground.
2. Average precipitation drops rapidly after October 15 - unfavorable for best action of herbicides.
3. Precipitation and te' iperature in May are favorable for start of active plant growth, and conditions remain favorable
through September.
The next step is to decide the best dates of desiccant application and the herbicide to use:
1. The choice of desiccation treatment lies between use of pellets that will penetrate the canopy and act as a soil
application, or use of a defoliant spray followed in 4 to 6 weeks by a desiccant spray aimed at the understory.
2. The best period for soil application of herbicide is late April or early May. Later applications stand too much
chance of loss from heavy leaching rains. The best spray period is from June through September, whenever clear
weather allows spraying to procede.
3. A soil application (before June 1) will drop leaves to the ground and leave them under hot, moist conditions
for4 to 5 months. A defoliant spray (August 1) and a desiccant spray (September 15) will cut the period when
leaves are on the ground by at least 2 to 3 months.
4. The best choice is the foliar spray, to reduce loss of leaf litter. At each spray date apply a mixture of 2,4- D
and 2,4,5-T (8 pounds, a.e. per acre) and picloram (2 pounds, ae., per acre) in diesel oil to make a total volume
of 5 gallons per acre.
IGNITION TECHNIQUES
In addition to treating live vegetation with desiccant chemicals, and timing incendiary operations to take every possible
advantage of the weather, forest fires can be made to spread more rapidly and bum more intensely by igniting many
small fires in a predetermined pattern. This technique, known as multiple igniti, utilizes the fact that two approaching
flame fronts will interact and reinforce each other. To see how multiple ignition works, let's look first at a fire asit
develops from a single ignition, and then at what happens when we set two fires properly spaced.
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