A century before President Trump announced the creation of a U.S. Space Force, another new military force was leaving the Earth. The Royal Air Force came into existence 100 years ago, on what might seem an inauspicious date, April Fool’s Day, 1918.

On that morning, my grandfather, John Everard Gurdon, flew on the RAF’s first ever patrol, hunting Luftwaffe aircraft in the skies over northern France. When he returned to his base at Vert-Galant, his fellow men of the 22 Squadron gathered in front of Gurdon’s Bristol F.2b fighter for a memorial photograph. The result (above) is in the Imperial War Museum now, and copies are all over the place.