The U.S. military attempted to control time and turn it into a weapon:

The US military attempted to control weather conditions and turn them into a weapon during the Vietnam War, a controversial effort that led to unintended consequences. According to reports from Croatian media, this experiment was part of a classified operation known as Operation Popeye, which aimed to increase rainfall in specific regions to disrupt enemy supply lines. The initiative, conducted between 1967 and 1972, marked one of the earliest attempts by a nation to manipulate atmospheric conditions for strategic military advantage. Throughout history, weather has played a decisive role in the outcome of major battles. Heavy rains, harsh winters, or strong winds have often altered the course of wars more than the number of soldiers or quality of weapons. This historical context explains why some nations have sought to harness natural forces under their command. During the Vietnam War, the United States took this idea further by launching secret operations designed to influence local climate patterns. One of the most notable examples of such efforts occurred during the Battle of Agincourt in 1415, where heavy rain turned the battlefield into mud, hindering French knights and contributing to the English victory. A similar situation unfolded at the Battle of Waterloo in 1815, where poor weather slowed Napoleon’s army and allowed Prussian reinforcements to arrive. Napoleon's disastrous campaign against Russia in 1812 also saw his troops decimated by severe winter conditions. Even the Mongols faced setbacks when their fleets were destroyed by typhoons during their attempt to invade Japan in the 13th century, an event later referred to as the “divine wind.” Unlike earlier commanders who had to accept prevailing weather conditions, the US military during the Vietnam War actively sought to alter them. Between 1967 and 1972, the American Air Force carried out a covert operation called Operation Popeye, officially named Intermediary-Compatriot. Its goal was to extend the monsoon season over areas through which North Vietnamese supply routes, known as the Ho Chi Minh Trail, passed. The objective was straightforward: heavy rainfall would transform roads into mud, impeding the movement of supplies, equipment, and troops. Operation Popeye was executed by the Fourth Meteorological Reconnaissance Squadron of the US Air Force. An unofficial slogan used by the unit was “We make mud, not war.” According to available records, the operation reportedly extended the monsoon season in certain areas by more than a month. The technique employed was cloud seeding, a method developed accidentally in 1946 and later refined by writer Kurt Vonnegut’s older brother, Bernard Vonnegut. Cloud seeding involves using tiny particles of silver iodide to stimulate the formation of ice crystals within clouds, increasing the likelihood of precipitation. Physicist Jan Balajka from the Technical University of Vienna explained that the ability of silver iodide to induce ice formation in clouds is not solely due to its crystalline structure but also because of atomic-level changes on the material’s surface. The US Air Force conducted approximately 50 cloud-seeding experiments and reported that in about 82 percent of cases, precipitation was recorded after intervention. Despite these successes, managing weather proved far more complex than anticipated. A US military official, who wished to remain anonymous, told The New York Times in 1972 that numerous errors occurred during the operation. He described how, during one mission, they inadvertently triggered around 178 millimeters of rainfall in just two hours above one of their special forces camps. Such incidents underscored the unpredictable nature of weather modification, even with advanced technology. Other nations have also experimented with altering weather patterns for strategic purposes. Britain conducted Project Cumulus between 1949 and 1952, but the program was halted after devastating floods hit the town of Lynmouth. China, too, has been reported to have used weather-modification technology, particularly during the 2008 Beijing Olympics, where authorities allegedly attempted to ensure favorable weather conditions. These efforts highlight a global trend of exploring technological means to influence environmental factors for national interests.