That Saturday, May 5, 1945, promised to be a beautiful spring day for Reverend Archie Mitchell, his pregnant young wife Elsie and the five children from the parish of Bly, Oregon, who were accompanying them on a picnic in the woods. As he parked the car at Leonard Creek, on Gearhart Mountain, the attention of his wife and the schoolchildren was caught by a curious object that had apparently fallen from the sky. As soon as they set about handling it, its sudden explosion killed Elsie Mitchell, Jay Gifford, Edward Engen, Dick Patzke, Joan Patzke and Sherman Shoemaker, leaving Pastor Mitchell as the sole survivor.

Operation "Fu-Go" had just claimed the first and only victims of the Second World War on the North American continent. They had been killed by one of some 9,000 balloon bombs launched from the east coast of the Japanese island of Honshu, designed to fly over the Pacific before dropping their incendiary explosive cargo on the United States.

These devices were powered by a secret weapon, known at the time only to Japanese scientists and military personnel: jet streams, powerful high-altitude winds that generally sweep across the planet from west to east. Early in 2023, these currents once again carried mysterious balloons, this time from China, over the United States. These impetuous winds "determine day-to-day meteorology across the globe," said Robert Vautard, director of the Institut Pierre-Simon Laplace (IPSL), where researchers are exploring if jet streams could become more threatening to human activities as a result of global warming. Europe would be potentially more vulnerable to catastrophic blockages of weather systems in a given region – summer heat waves, like this summer's infernal heat domes, but also winter floods – linked to the jet stream affected by climate change.

First studies published in Esperanto

In 1945, the science of jet streams was still in its infancy. With good reason: Their discoverer, meteorologist Oishi Wasaburo (1874-1950), director since 1919 of the aerological laboratory at Tateno (now Tsukuba), was also director of the Japanese Esperanto Institute. As such, he made it a point of honor to publish his work only in this "universal" language invented at the end of the 19^th century by Louis-Lazare Zamenhof. The 1,246 pages of his 19 reports published between 1926 and 1944 are written in this vernacular, including his 1926 Raporto de Aerologia Observatorio de Tateno, which records his first observations of strong westerly winds at high altitudes over his aerological station in winter. Like those that followed, they were ignored by his Western counterparts.

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