Conventional prompt global strike (CPGS) is a military option under consideration by the U.S. Department of Defense. This book, the final report from the National Research Council’s Committee on Conventional Prompt Global Strike Capability, analyzes proposed CPGS systems and evaluates the potential role CPGS could play in U.S. defense. U.S. Conventional Prompt Global Strike provides near-, mid-, and long-term recommendations for possible CPGS development, addressing the following questions: Does the United States need CPGS capabilities? What are the alternative CPGS systems, and how effective are they likely to be if proposed capabilities are achieved? What would be the implications of alternative CPGS systems for stability, doctrine, decision making, and operations? What nuclear ambiguity concerns arise from CPGS, and how might they be mitigated? What arms control issues arise with CPGS systems, and how might they be resolved? Should the United States proceed with research, development, testing, and evaluation (RDT&E) of the Conventional Trident Modification (CTM) program5 and, ultimately, with CTM production and deployment? Should the United States proceed with the development and testing of alternative CPGS systems beyond CTM?