he paper examined Southeast Asia as a whole and focused on similarities among countries composing what is now known as the Association of Southeast Asian Nations (ASEAN). In order to determine these similarities, the analysis focused on the fact that during World War II the whole of Southeast Asia was occupied by one political power: Japan. The policies the Japanese implemented in the region were to a degree very similar in terms of pressures and tensions that occurred in the different countries. The paper argues that these pressures and the responses of the various peoples of Southeast Asia instilled a nucleus of common identity in Southeast Asia as a whole. Basically, the policies that the Japanese implemented all over Southeast Asia were the following: the setting up regional administrations; the extraction of resources and emphasis on local self-sufficiency; the implementation of cultural Japanization; and local indigenization policies. The Southeast Asian responses that crystalized this joint Southeast Asian identity may be described as: accommodating and resisting the Japanese; commemorating portraying; and collectively remembering the era. The process of action and reaction between Japan and Southeast Asia was formative of this joint Southeast Asian identity.