With Operation Popeye, the U.S. government made weather an instrument of war

Troops wade through a river in Vietnam. Wikimedia Commons

It was a seasonably chilly afternoon in 1974 when Senators Claiborne Pell, a Democrat from Rhode Island, and Clifford Case, a Republican from New Jersey, strode into the chambers of the Senate Committee on Foreign Relations for a classified briefing. While the meeting was labeled “top secret,” the topic at hand was rather mundane: They were there to discuss the weather. More specifically, Pell, the chairman of the now-defunct subcommittee for Oceans and International Environment, and his colleague were about to learn the true extent of a secret five-year-old cloud seeding operation meant to lengthen the monsoon season in Vietnam, destabilize the enemy, and allow the United States to win the war. Though it cycled through several names in its history, "Operation Popeye" stuck. Its stated objective—to ensure Americans won the Vietnam War—was never realized, but the revelation that the U.S. government played God with weather-altering warfare changed history. The Nixon administration distracted, denied, and, it seems, outright lied to Congress, but enterprising reporters published damning stories about rain being used as a weapon, and the Pentagon papers dripped classified details like artificial rain. Eventually, the federal government would declassify its Popeye documents and international laws aimed at preventing similar projects would be on the books. But the public would, more or less, forget it ever happened. Given the rise of geo-engineering projects, both from municipal governments and private companies, some experts believe Popeye is newly relevant.

A radarscope featured in the Compendium of Meteorology, 1951. Internet Archive Book Images via Flickr

Most travel agents would recommend planning your visit to Vietnam roughly between the months of November and April. Prices tend to jump during the so-called high season, but it’s the only surefire way to avoid the rain. And, boy, is there rain. Between roughly May and October, the mercury rises to 90 degrees and the humidity can hit 90 percent. Heavy with water and churned by reversing monsoon winds, the northern metropolis of Hanoi typically receives 8.2 inches of rain in July alone, while Ho Chi Minh City in the south, where the monsoon hits a little later, racks up an average 11 inches each September. (For comparison, the southwestern state of Arizona typically gets 8.04 inches of rain in a year.) Back in the 1960s, however, Vietnam’s rainfall patterns weren’t the concern of American tourists, so much as the American military. When preliminary tests for Operation Popeye began in October 1966 under President Lyndon B. Johnson, the Vietnam War had been underway for over a decade (though still a decade away from its somber conclusion) and more than 8,000 Americans had already died. With traditional methods failing, the U.S. government decided to look to the skies. “The close monitoring of troop and truck traffic along routes where rain had fallen verified beyond any doubt the naturally adverse effects of rainfall and accumulated soil moisture on the enemy’s logistic effort,” Lieutenant Colonel Ed Soyster told Senators Pell and Case, according to the declassified notes from that 1974 meeting. Operation Popeye, he continued, intended to further ruin roads, jam rivers, and extend the amount of time swathes of Vietnam weren’t traversable.

The cloud seeding process can be done from an airplane or with a generator on the ground. Wikimedia Commons

Cloud seeding is a method for artificially stimulating precipitation, like rain or snow. The practice is thought to have originated in 1946. While experimenting with dry ice, Vincent Schaefer, a self-taught chemist employed by General Electric, made a big discovery. He noticed that cloud condensation nuclei—the tiny particles around which water condensates—could be artificially produced to create rain and snow. Schaefer put his discovery to the test by “seeding” the clouds over the Berkshire Mountains in Massachusetts and successfully created precipitation. “He was hailed as the first person to actually do something about the weather and not just talk about it,” the New York Times wrote in his obituary. Of course, Schaefer’s discovery was not met with enthusiasm alone. While some dreamed of ending drought (or, as the Times drolly notes, ensuring white Christmases until the end of time), others worried that rain would be “stolen,” as scientists pulled precipitation out of clouds in some places and not others. At first, no one seemed to consider the wartime applications of cloud seeding, but on March 20, 1967, the “operational phase” of Popeye began. Pilots and their crew would soar over select regions of Vietnam with a canister of silver or lead iodide, which were, by the 1960s, considered two of the primary sources of water condensation nuclei. The plane crew would ignite the canisters and release particle-rich smoke into an existing storm. If all went well, the jolt of artificial nuclei would reverberate through the system, forcibly spurring additional precipitation. Despite 80 years of cloud seeding efforts, rigorous research aimed at proving (or disproving) its efficacy is still underway. During their top secret briefing on Popeye, Senators Pell and Case were told that though U.S. taxpayers paid, without their knowledge, some $3.6 million a year for such operations over Vietnam (or about $23 million a year in today’s dollars), Popeye’s success was “certainly limited” and also fundamentally “unverifiable.” As he digested these facts—processed the full extent of the secret wartime weather manipulation project—Senator Pell seemed increasingly indignant, as documented in the official meeting report. Why, he asked, was it kept secret? And what other secrets were there? “The thing that concerns me,” Pell said, “is not rainmaking per se, but when you open Pandora’s box, what comes out with it?” When the details of Operation Popeye were made public a two months later, on May 19, 1974, many Americans—as well as our allies and enemies abroad—were left pondering the same question.

A plane, photographed in 1964, reportedly used in domestic cloud seeding efforts. Wikimedia Commons

In the 1960s, another experimental weather-modification operation was underway. Called Project Stomfury, the military deployed pilots (pictured here) armed with silver iodide in the hopes of weakening damaging tropical storms. NOAA