Koji Iizuka (1906_??_1970) is a Japanese geographer, who introduced French school of geography to Japan, attempting to bring about a revolution in human geography in Japan. He continued to make various comparative studies on culture, being deeply conscious of his country's fluctuating situations. After World War II he played an important and leading role in the development of democratic principles in Japan. In this paper the writer reviewed Iizuka's research activities from 1930 to 1945. The writer divided this period into six parts, and described how Iizuka did his research activities under different circumstances. I. Just before and during his study in France (April, 1930 December, 1934) Iizuka appreciated that P. Vidal de la Blache's “Principes de Geographie Humaine” was based on bionomical method. Being attracted by this book, he decided to study, in France, geography as social science. In France he had a new understanding of cultures of Europe and Japan. Moreover, he clearly understood the position of Japan in the world just after the Manchurian Incident. II. Just after his return to Japan (January, 1935_??_March, 1938) Although he was much concerned about critical conditions inside and outside our country, he devoted himself to writing the results of his study in France and published two writings “79 Degrees North” and “Problems in the History of Human Geography.” III. During the China Incident (April, 1938_??_March, 1941). He felt that the war between China and Japan was essentially the Japanese invasion. So, he decided to go on with his work, trying not to be swayed by the situation. For that reason, he chose the work of translating Vidal de la Blache's “Principes de Geographie. Humaine” and L. Febvre's “La Terre et l'Evolution Humaine” into Japanese. IV. Just before and after the outbreak of the Greater East Asia War (April, 1941-March, 1942) He changed his attitude, and began to participate in the situation because he felt a critical moment that the United States with overwhelming economic power and Japan were confronted each other. He supported the outbreak of the war because he thought that the war was actually between Japan and the United States which was a imperialistic country, and that Japan had marked a period of exultant aggression at the beginning of the war. He thought that the Greater East Asia Co-Prosperity Sphere must be realized. Therefore, he proposed that it was necessary for Japan to be more industrialized, and for the Sphere to be reorganized, making use of the actual circumstances in this Sphere. V. In the middle of the Greater East Asia War (Summer, 1942_??_Spring, 1943) While he supported the formation' of the Greater East Asia Co-Prosperity Sphere, his studies were away from the main current of the time. Among his studies were criticism on geopolitics, the history of contacts between different cultures, and the progress of geographical theories and the change in world view. VI. In the latter half of the Greater East Asia War (Summer, 1943_??_Summer, 1945) He anticipated the defeat of Japan. It was appeared in the following points. 1) He made it clear, by studying a comparison of civilizations, that Japan had not reached modern civilization. 2) He criticized theoritical studies of geography in Japan. 3) He criticized the irrational administration systems and the feudalistic moral civilization of Japan. However, he made these remarks while supporting the formation of the Greater East Asia Co-Prosperity Sphere. He did not expect a social reform after the war. It can be said that his way of participation in the situations is characterized as follows 1) He did not resist the internal order. Even if he sometimes criticized the administration, it was done within the limits of the order. 2) He tended to make the situations objects of study.