A leader of the Doubting Antiquity Movement of the 1920s, Gu Jiegang (1893–1980) was well known for his cultural iconoclasm. But in the 1930s, he experienced a drastic change in his intellectual life. Partly in response to Japanese expansion in Manchuria and northern China, Gu no longer practised “learning for the sake of learning.” Instead, he used his academic writings to mobilize his fellow countrymen to defend their nation. As a result, he changed both the purpose and the content of his academic writings. Unlike his previous works which challenged the Confucian orthodoxy, he affirmed the Chinese tradition. Rather than exposing the hypocrisy of national memory, he participated in creating a collective memory for national resistance. In this paper, the author examines these changes in Gu’s thoughts and links them to the broader context of the Sino-Japanese War (1937–1945).