<i>Nihon Sekigun</i> (the Japanese Red Army) is an extreme left terrorist group which originated from the university disputes in the late 1960's. There is no single systematic study on this subject with the result that specialists on terrorism often make inaccurate remarks concerning <i>Nihon Sekigun</i>. This thesis is the first attempt to analyze the activities of the group. For this reason, a considerable portion of the work is allocated to fact-finding, which concludes with the following points. (1) <i>Nihon Sekigun</i> is an anomaly or mutation of Japanese society, and not a product of Japanese cultural or social backgrounds, as some scholars have indicated. (2) The reason for the group's decline is its lack of popular support or sympathy, and therefore, its operational bases were predominantly outside the country. (3) Contrary to some experts' remarks, evidence indicates that the group did not enjoy positive state-sponsorship from any country. (4) The group's cooperative relationship with other extremists outside Japan has been found to be extremely superficial. (5) The Japanese Government constantly conceded to the group's demands at each hostage-taking incident but these concessions were in line with the desired actions that other states wanted Japan to follow. (6) The threat posed by the group to Japanese and international society was within tolerable limits. (7) It is unlikely that the group will undertake any major terrorist operations in the foreseeable future.