Japanese mapping in the Asia-Pacific region up to 1945 calls for scrutiny, because its development was a multifaceted process with military, administrative, political, and cultural dimensions. This article traces the changes in Japanese mapping of overseas areas to the end of World War II and assesses the significance of the resulting maps, called gaihōzu, as sources for East Asian history. As implements of military operation and colonial administration, the gaihōzu were produced during a protracted period by various means under changing circumstances. Expanding military activity also promoted differentiation among the gaihōzu by increasing the use of maps originally produced in foreign countries. In conclusion, the need for detailed cataloging, in combination with chronologically arranged index mapping, is emphasized for the systematic use of the gaihōzu.Cross-Currents: East Asian History and Culture Review E-Journal No. 2 (March 2012) • (http://cross-currents.berkeley.edu/e-journal/issue-2) 2009; Butlin 2009, 325-349). Particularly intensive studies of historical cartography concerning the former British colonies have been carried out (Barrow 2008;Edney 1997;Stone 1995). These studies suggest that similar frameworks are applicable for historical study of cartography in other areas.Japanese mapping in the Asia-Pacific region up to 1945 is a typical case that calls for scrutiny of this kind. After the Meiji Restoration, Japan made continual efforts to extend its cartographic knowledge of surrounding areas as well as to upgrade the techniques of its surveyors. Modern surveying methods, including triangulation and aerial photogrammetry, were applied extensively in the later phase (Kobayashi 2011). After Taiwan and Korea were annexed, colonial governments produced thematic maps covering hydrography, geology, soil, industry, population, and urban planning in addition to topographical maps of the territories (Sŏul Yŏksa Pangmulgwan 2006;Wei et al. 2008). Meanwhile, maps designed for the general public documented the expanding sphere of influence of the Japanese empire and the progress of its battles, which followed one after another. Bird's-eye views of the colonies and their cities were also actively produced, carrying on the early modern tradition of Japanese commercial mapmaking (Zhuang 1996). The development of Japanese overseas cartography during these decades was a multifaceted process with military, administrative, political, and cultural dimensions. It represented neither a simple accumulation of geographical intelligence