This book addresses the issues raised by Chinese and North Korean maritime ‘gray zone’ activities in the Indo-Asia-Pacific region. For years, China has been harassing its neighbors in South China Sea and East China Sea, employing both coast guard and maritime militia forces, in the name of safeguarding Chinese sovereignty. This behavior is frequently characterized as constituting ‘gray zone’ activity. As the term suggests, this refers to a state of conflict that falls between peace and war. Interestingly, the Yellow Sea, which is geographically much closer to China than South China Sea or East China Sea, has been comparatively quiet. However, there is a danger that the PRC has the capability to replicate its gray zone activities in this area. Worse, North Korea has also been engaging in carefully-calibrated provocations there. This book addresses pressing questions about these activities and offers: (1) a conceptual framework to understand maritime gray zone operations and Beijing and Pyongyang’s approach, with an unprecedented focus on the Yellow Sea; (2) a comprehensive, fully updated fleet force structure for the PRC’s Coast Guard, together with projections regarding how the Coast Guard is likely to develop in the future; (3) an extensive organizational analysis of the PRC’s Maritime Militia that surveys the many units relevant to Yellow Sea operations, some revealed publicly for the first time; and (4) a detailed assessment of North Korean maritime ‘gray zone’ activities. This book will be of great interest to students of naval strategy, maritime security, Asian politics, and international security.