The vulnerability of surface ships to aerial attack was established decisively during the Second World War, when aircraft rendered even heavily armored vessels vulnerable to coordinated air assault. What has changed is not the vulnerability itself, but the scale and proliferation of systems that exploit it. Where aerial attack was once constrained by the availability of piloted aircraft, it is now enabled by systems that are unmanned, low-cost, more numerous, and more easily distributed. The result is not a new paradigm, but a return to an old one under conditions of far greater scale. This article examines the impact of this change at the level of naval defensive systems, focusing on current U.S. naval point defense systems and the constraints that govern their effectiveness. Battleship HMS Prince of Wales sinking after air attack – December 10, 1941 The Arithmetic of Warship Aerial Defense Modern warships have layered defensive systems capable of intercepting incoming aerial threats at multiple ranges.…