The U.S. military’s history of encounters with unidentified flying objects goes back to World War II. One of the first major UFO sightings came in 1942, when anti-aircraft batteries around Los Angeles opened fire at objects in the sky that they thought were Japanese aircraft. The Army determined later that a lost weather balloon had caused a false alarm.

Later in the war, pilots with the Army’s  415th Night Fighter Squadron reported seeing strange discs of light over Germany, which they dubbed “Foo Fighters” — a term that came from the Smokey Stover firefighter cartoon.

And two years after the war ended, a high-altitude balloon meant to monitor for Soviet atomic bomb tests crashed near Roswell, New Mexico. Based on an Army major’s comments, the local newspaper reported that a “flying saucer” had been recovered, giving birth to the modern phenomenon of UFO sightings.

While both military and civilian observers have pondered these encounters for decades, the Pentagon’s focused efforts to find out what UFOs are only started gaining momentum in 1947, when the Air Force launched Project Blue Book.

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