This chapter examines the formative role of war in shaping generational experience in China in the first half of the twentieth century. The First World War, by exposing China’s fragility on the global stage, deepened national disillusionment and gave rise to the May Fourth Generation of intellectuals who sought cultural and ideological renewal. Yet despite their reformist zeal, much of Chinese society remained bound by familism and localism. Only with the outbreak of the Anti-Japanese War—a total war that reached every corner of society—did revolutionary change penetrate everyday life. The generation forged in these upheavals —the war youth generation—embodied a new ethos of collectivism, sacrifice, and ideological conviction, marking the transition from a world organized by kinship to one unified by revolutionary purpose, providing the social foundation for the Communist Party to mobilize the masses and redefine the meaning of citizenship and collective belonging at the time of the establishment of the new communist regime. The chapter concludes by examining how the epic generation of May Fourth vanguards and the more silent war youth generation, through their contrasting and related generational identity, jointly forged the intellectual and social foundations of a new China.