Forget Bush’s National Missile Shield. The best military defense is a Russian winter. It got the better of King Charles XII of Sweden, sent Napoleon packing, and eventually shooed Hitler away. A few years after that, though, it was the Germans that were favored by the weather gods—for weeks, Patton’s Third Army was stuck near the edge of Germany, plagued by rain that kept American tanks and trucks and soldiers in place. The general’s solution? A prayer to those gods:

Almighty and most merciful Father, we humbly beseech Thee, of Thy great goodness, to restrain these immoderate rains with which we have had to contend. Grant us fair weather for Battle. Graciously hearken to us as soldiers who call upon Thee that, armed with Thy power, we may advance from victory to victory, and crush the oppression and wickedness of our enemies and establish Thy justice among men and nations.¹

Patton was certainly not the first military leader to beseech His Great Goodness for favorable conditions. When Hannibal invaded Italy in 217 BC, he waited for the marshes to freeze so his mounted troops could pour in. In 1776, the harsh winter helped George Washington’s army, letting it move quickly across the frozen Delaware River. And in 1941, the Japanese essentially hid their aircraft carriers moving toward Pearl Harbor in a large Pacific storm.

But, to paraphrase Mark Twain, everybody prayed about the weather, but nobody did anything about it. That changed in 1946, when General Electric scientists Vincent Schaefer and Irving Langmuir created an artificial cloud by introducing dry ice into a freezer, and then developed a technique for “cloud seeding,” still used today.

By the late 1950s, people began to think about our new ability to alter the weather in military terms. The Cold War was kicking into high gear, and the US intelligence community became aware that the Soviets were experimenting with cloud seeding and other kinds of weather control, such as cloud dissipation. In 1957, Henry Houghton, chair of MIT’s meteorology department, noted, “I shudder to think of the consequences of a prior Russian discovery of a feasible method for weather control.”² That same year, a Presidential Advisory Committee on Weather Control noted (with perfect deadpan sensationalism) that, “weather modification could become a more important weapon than the atom bomb.”³ The weather race, though never as fierce or as public as the space race or the arms race, was on. (The Soviets really were working on weather, with the hopes of, among other things, warming its vast northern regions and removing the ice in the Arctic Sea.)

That any new technology that could be used as a weapon would be used as a weapon now seems obvious—a kind of first principle of warfare—but it is a relatively recent idea, a product of the “total war” strategy of the two world wars, where tactics and weaponry became increasingly more destructive. And there was historical precedent for offensive uses of the environment. During the Franco-Dutch War of 1672–1678, for example, the Dutch breached the dikes around Amsterdam, flooding part of the low-lying country and putting the French on the defensive. (The Dutch won.)

With the political and military stage set, the US got to work on figuring out how to alter the weather, and what to do with that knowledge. Much of the work seems to have been done at the Navy’s China Lake weapons research center. “Between 1949 and 1978,” the base’s in-house newspaper, The Rocketeer, reported, “China Lake developed concepts, techniques, and hardware that were successfully used in hurricane abatement, fog control, and drought relief.”⁴

“Drought relief” is an interesting way to put it. China Lake’s research caught the eye of the CIA in the early 1960s, which saw the potential of weather control in the rapidly expanding conflict in Vietnam. The CIA’s first use of the Navy’s technology was crowd dispersal. “The Diem regime was having all that trouble with the Buddhists,” an agent told Seymour Hersh in 1972. “They would just stand around during demonstrations when the police threw tear gas at them, but we noticed that when the rains came they wouldn’t stay on. The agency got an Air America Beechcraft and had it rigged up with silver iodide. There was another demonstration and we seeded the area. It rained.”⁵

In 1966, the idea of raining on Vietnam became the top-secret Project Popeye, which ran for some seven years and included more than 2,600 cloud-seeding flights over Vietnam and Laos. The objective was simple: Make rain that would make or keep the Ho Chi Minh Trail—a main supply route for the North Vietnamese—so muddy that it was unusable. (Why “Popeye”? The artificially created rain was apparently called “Olive Oil.”)

The story of the top-secret project—flown by the Air Force but controlled by the CIA and the White House—was broken in 1971 in Jack Anderson’s national newspaper column, then, to greater fanfare, in July 1972, with Hersh’s front-page story in the New York Times. And while there were no rules at the time about weather modification—or any environmental warfare, for that matter—the Nixon administration was not happy with Hersh’s revelations. The White House and the State Department declined comment, and one unnamed official said, “This is one of those things where no one is going to say anything.”⁶ (People said even less about CIA weather modification in Cuba. During 1969 and 1970, planes from China Lake seeded clouds that rained over non-agricultural regions of Cuba, leaving at least some of the country’s sugar cane fields dry.)

The eventual response was an international treaty, the Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques, or ENMOD, which entered into force in 1978. The main tenet of the treaty, which stands today, is this: “Each State Party to this Convention undertakes not to engage in military or any other hostile use of environmental modification techniques having widespread, long-lasting or severe effects as the means of destruction, damage or injury to any other State Party.”⁷

Weather control activities seem to have quieted down after ENMOD, but fortunately for the US military, the treaty has a loophole big enough to drive a truck through: It prohibits only action with “widespread, long-lasting or severe effects.” When Air Force intelligence analysts turned their thoughts to the weather in the mid-1990s, they made up their own definition of these limits: widespread means affecting more than several hundred kilometers; long-lasting means for a period of months; and severe “involves serious or significant disruption or harm to human life, natural or economic resources, or other assets.”⁸ Which is to say that, except for the human life part, most military applications, which tend to be short-term and localized, are allowed. These analysts’ conclusions are contained in an extraordinary report, published in 1996, called “Weather as a Force Multiplier: Owning the Weather in 2025.” If the US intelligence community did ignore the weather for a while, “Owning the Weather” certainly made up for it. Envisioning a world where technology has made control over the local weather phenomena much more precise—and where a global network of sensors has greatly increased available atmospheric data—the writers declare that in three decades time, “US aerospace forces can ‘own the weather,’” and “shape the battlespace in ways never before possible.”⁹

While “Owning the Weather” relies primarily on extensions of existing weather modification techniques, the authors strike more boldly into the future with speculation about nanotechnology-based “artificial weather.” “A cloud, or several clouds, of microscopic computer particles,” they note, “all communicating with each other and with a larger control system could provide tremendous capability. Interconnected, atmospherically buoyant, and having navigation capability in three dimensions, such clouds could be designed to have a wide range of properties.”¹⁰

At times, the Air Force report reads like a declaration to violate the ENMOD agreement. The authors even note that the only reason they don’t discuss more serious weather control—made-to-order weather, large-scale climate modification, control of storms, etc.—is that it won’t be technically feasible by 2025. “Such applications would have been included in this report as potential military options,” they note, “despite their controversial and potentially malevolent nature and their inconsistency with standing UN agreements to which the US is a signatory.”¹¹

Why is the United States so interested in the weather that it would violate international treaty? The answer may lie more in the psyche of the government than in specific tactical advantages. The US military has long been used to having a stacked deck. The US Navy once owned the seas; later, the Air Force had the run of the skies. For a while, our sole possession of the atomic and hydrogen bombs gave us the “ultimate” weapon. Dominion over the atmosphere might be the next “ultimate” weapon, proof not only of military invincibility but perhaps, finally, of Divine Right.