Abstract : One of the most salient trends in military technology is the growing prominence of unmanned vehicles. Much has been written about Unmanned Air Vehicles (UAVs), and a fair amount about Unmanned Surface and Unmanned Ground Vehicles (USV/UGVs). In contrast, very little has been written about Unmanned Undersea Vehicles (UUVs). This paper contends that UUVs, currently most prominent as ISR assets and as capability-augmentation to other platforms, will come into their own as an independent combat capability, creating operational and strategic level effects. Through their inherent asymmetry, UUVs will deliver powerful capability to lower-tier navies and even non-state actors. Without anticipatory planning, and perhaps even despite it, top-tier state actors such as the U.S. will find themselves challenged in their ability to counter the threat of "sea denial" posed by UUVs. UUVs could have major effect on the operational level of war, by challenging many key assumptions around which campaign planners have based their planning.