May 5, 1945. A minister and his pregnant wife take five kids from their Sunday school on a picnic in the woods near Bly, Oregon. Within minutes, six of them are dead. They were killed by a weapon launched from Japan, more than 5,000 miles away. Most Americans have never heard of it. By late 1944 Japan was losing badly. It wanted a way to hit the American mainland, and it came up with one of the strangest weapons of the war. Balloons. Huge ones, more than 30 feet across, made from thin paper glued together in layers. A lot of that work was done by Japanese schoolgirls. The balloons were filled with hydrogen and loaded with bombs and incendiaries. Then they were released into the jet stream. Riding winds high over the Pacific, they could cross to North America in about three days. A clever system of sandbags and altitude sensors kept them at the right height. When the ballast ran out, the bombs dropped. The goal was to start massive forest fires and spread panic. Japan launched around 9,000 of them. Hundreds reached North America. They turned up in Oregon, Washington, California, Montana, Canada, even as far as Michigan and Mexico. And Americans heard almost nothing about them. The US government asked newspapers and radio to stay quiet. If the Japanese never heard about balloons landing, they'd assume the program had failed and stop. It worked. Japan eventually did shut it down. But the silence had a cost. That morning in Oregon, Reverend Archie Mitchell stopped the car to park. His wife Elsie, five months pregnant, walked ahead with the kids. They were between 11 and 14 years old. They found something strange in the woods. A big deflated balloon with a strange device hanging from it. Archie heard someone call out to him to come look. Then it exploded. Elsie and all five children were killed. Archie survived. Nobody had ever warned them, because nobody in America was supposed to know these things existed. Elsie Mitchell, Joan Patzke, Dick Patzke, Jay Gifford, Edward Engen, and Sherman Shoemaker became the only people killed by enemy action on the American mainland in all of World War Two. Only after their deaths did the government start warning the public not to touch strange objects in the woods. The story doesn't end there. Archie Mitchell later remarried. His new wife was the older sister of two of the children who died that day. They became missionaries and moved to Vietnam to work at a leprosy hospital. In 1962, Viet Cong guerrillas raided the hospital and took Archie away. He was never seen again. Decades after the war, a group of Japanese women who had built the balloons as schoolgirls learned what their work had done. They folded a thousand paper cranes and sent them to Bly, Oregon, with an apology. There's a monument in the woods today, at the spot where it happened.