From the beginning of the Sino-Japanese War in 1937 to the end of the WWII in 1945, Japanese military occupied wide areas in East and Southeast Asia and the Western Pacific. Along with the extension of the front, Japanese military's weather surveys replaced existed local ones and interrupted their continual observation. In addition to ground observation, it carried out upper-air observation with pilot-balloon and radiosonde to support its air forces on the basis of the extended survey network. As for the data accumulated up to the end of the WWII by Japanese military, however, it has been believed that they were lost in the disturbances of war and to restore this wartime discontinuity is almost impossible.
Scrutinizing book stocks of several institutions at home and in the United States, such as the Library of Congress, the author found not a few unused materials, in which wartime weather data had been recorded. In this paper, following up the wartime vicissitudes of Japanese weather survey, he reviewed instructive cases, where such materials had been rescued successfully, in order to promote the efficient search of buried data in the near future.