The Sino-Japanese dispute over the Ryukyu (Liu-ch'iu or Liuqiu) Islands is an important academic subject but has so far received little attention from scholars in the Western world. The present exhaustive study, by using a multi-archival and multi-lingual approach, uncovers for the first time the inner and full story of one of the most complicated and controversial diplomatic issues in modern East Asia. The dispute arose because both China and Japan laid claim to the Ryukyu Islands based on different grounds, leading to the prolonged crisis of half war and half peace between the two countries-a "quasi-war"-from 1871 to 1881 and beyond, with profound global implications. Today, over a century later, the "quasi-war" still continues as China and Japan once again engage in another island dispute, this time over the Senkaku (Tiaoyutai or Diaoyutai) Islands-a related issue to the Ryukyu problem. Thus, the "quasi-war" is still very much alive in East Asia even in the early 21st century. Dr. Edwin Pak-wah Leung is Professor of Asian Studies at Seton Hall University in South Orange, New Jersey, USA. His academic interests include Asian politics and diplomacy as well as modern Chinese history. He has published over twenty books and numerous academic articles written both in English and Chinese. As an internationally known scholar, he has affiliated with many well-known universities such as University of California at Berkeley and Los Angeles, University of Michigan, Princeton University, Columbia University, University of Hong Kong, Chinese University of Hong Kong, Peking (Beijing) University, Zhejiang University, Wuhan University, and University of Tokyo. He has also received many awards, including the prestigious Ellis Island Medal of Honor.