If weather modification can actually turn the tide of battle remains an open question. The American military's only acknowledged recent experience in using weather as a weapon occurred with Project Popeye, which began in 1966. The experiment's objective was to extend the monsoon season, thereby increasing the amount of mud that formed on the Ho Chi Minh trail, a supply route that wound from what was then North Vietnam through Laos and Cambodia into South Vietnam. To produce the rain, a silver iodide rainmaking agent--dubbed "Olive Oil"--was dispersed from WC-130, F4 and A-1E aircraft into the clouds over the trail.

Positive results during the initial program led to its continued operation until 1972. But to this day, analysts remain divided over whether the rain created enough extra mud to significantly reduce the delivery of supplies. When you're slogging through ankle-deep mud, another inch of it probably doesn't make that much of a difference.