This thesis represents a new attempt to use numerous volumes of mostly unpublished diaries, viewed as private forms of ego documents, as the main source for examining identity-centered issues. Using the private diaries of two Taiwanese intellectuals, Chen Wangcheng and Wu Xinrong, I have examined how Taiwanese national consciousness emerged and was reconstructed under the Japanese and Chinese Nationalist rule between 1920 and 1955. The examined cases suggest that a sense of Taiwanese national consciousness was created in the 1920s via an empirical construction, on the one hand, through the working of the politico-social networks, and via an abstract construction through the spread of print-capitalism on the other. Nevertheless, between 1937 and 1945, this multi-dimensional Taiwanese national consciousness was primarily reconstructed by the war development and mobilization, which were also reinforced by war propaganda, such as the discourse of the (greater) East Asian new order, rather than by the Kōminka cultural and religious policies. In other words, the sense of cohesion between the Taiwanese and Japanese was intensified, mainly because they shared a common fate in the cumulative process of warfare. In general, the islanders maintained a double identity as 'Taiwanese/Japanese', with the former being visibly tilted towards the latter during the war. In the early postwar period, the reconstructed Taiwanese national consciousness underwent a further reconstruction caused by the regime change from Japan to China in 1945 and the 2.28 Incident in 1947. The Taiwanese experienced a new imagination of Chinese national consciousness during the regime change, which was later challenged by the misrule of the Nationalist Chinese government and led to the emergence of the bensheng ren (native Taiwanese) consciousness. In nature, the increasing ethnic confrontation between the bensheng ren and waisheng ren (mainlanders), which centered around the conception of 'modernity vs. nationality', mainly resulted from their opposing 'Japanese experiences' and finally led to the outbreak of the 2.28 Incident, which in reverse provided a political focus to materialize the bensheng ren (vs. waisheng ren) identity from outside. In addition, the emerging international Cold War environment enabled the creation of a de facto independent state based on Taiwan-size governance, which internationally had an evident impact on shaping and reshaping the bensheng ren identity.