The Space Force, the sixth and newest branch of the U.S. military, was authorized by Congress and signed into law by President Donald Trump in December 2019. The initiative had been shaped within the armed forces and Congress over the previous 25 years, based on the premise that as satellite and space technologies evolved, America’s military organizations had to change as well. From the start, the Space Force had detractors. Air Force officials wondered if it was necessary, while some political observers believed that it signified the start of a dangerous (and expensive) militarization of another realm. What seemed harder to argue against was how nearly every aspect of modern warfare and defense — intelligence, surveillance, communications, operations, missile detection — has come to rely on links to orbiting satellites. The recent battles in Eastern Europe, in which Russia has tried to disrupt Ukraine’s space-borne communication systems, are a case in point. And yet the strategi...