The idea of an anti-ship ballistic missile has taken root in China's military planning. The country is not only building more of its first version of such a weapon, the DF-21D, but has developed an anti-ship warhead for another such missile, the more-numerous DF-26, billed as having a 2,500-mile range - more than enough to hit Guam from several hundred miles inland in China. In theory, that puts any naval adversary at risk long before it is in Chinese waters, let alone within striking distance of China's coastline. That puts US carrier strike groups - a linchpin of US power projection, able to hit any corner of the world at short notice with overwhelming force - in a situation they have never before faced. For years, US war planners took for granted that American naval power could operate unimpeded anywhere on earth and deliver strikes with relative impunity. If a missile can sweep that option off the board, it changes the balance of power not just in Asia, but across the globe. It is a collision of two world-shaking forces: China, the only country to build large numbers of ballistic missiles to threaten enemy fleets, and the United States, the only power on earth with more than a single nuclear-powered aircraft carrier. Neither situation seems likely to change in the near future, putting both countries on what may be a collision course of doctrine and technology. The only way an outside observer will know for certain how well the DF-21D and its successors work is if they are used operationally, in the face of the US Navy's growing array of countermeasures and anti-missile systems. If that happens, the world is either plunging into a catastrophic war, or several chapters deep into one. That makes the development, deployment and threat posed by the DF-21D and China's other ASBMs crucial to study. The outcome of the next great power conflict might hinge upon whether this type of missile truly is a Carrier Killer. AUTHORS: Gerry Doyle is an editor on the Global News Desk at Thomson Reuters. He has been posted overseas for 13 years, 10 of them in Asia, with a recurring focus on defense and security. A third-generation sailor, Blake Herzinger joined the Navy while studying political science at Brigham Young University. He first experienced Asia as an officer in the U.S. Navy deployed to Okinawa and moved to Singapore in 2013, completing a masters degree in strategic studies while serving as a naval liaison. He became a consultant to the U.S. Navy in the Asia-Pacific after leaving active service in 2017, but remains in the U.S. Navy Reserve. He writes regularly on naval matters and the Asia Pacific, with work published in Foreign Policy, Brookings, and War on the Rocks, and joined the Pacific Forum as a Non-resident WSD-Handa Fellow in 2021. 11 b/w photos, 60 colour photos, 16 colour profiles, 6 maps, 5 diagrams, 3 tables