President Trump’s recent directive to the Defense Department to create a new branch of the military, a United States Space Force, was not an idle musing. Trump’s proposal derives from a growing debate inside military and political circles about how to best meet the threat posed to American space assets by potential enemies: Russia and China, to be precise.Pentagon officials are sounding the alarm that the United States is not ready for a space war. The other two great space powers have been creating the weapons to achieve an orbital Pearl Harbor, the destruction of satellites that provide the military with communications, navigation, and intelligence capabilities it will need in a war. After years of neglect, the current administration is pouring resources into a fevered attempt to play catchup before it’s too late.The argument against a United States Space Force, at least at this time, is that creating it would be a massive reorganizational undertaking, complicating rather than enhancing America’s capability to fight a war in space in the near term. The argument for creating a space-faring branch of the military stems from the fact that the space environment is characterized by lack of air, extremes of heat and cold, microgravity, and the realities of orbital mechanics, which mean that no object remains in one place. The space environment is far different from the air, sea, and land where Americans are accustomed to fighting and hence needs a branch of the military trained and accustomed to operating in it.