Over the past decades, the nature of war has transformed from inter-state wars to intra-state conflicts. By the end of colonialism, many African countries, including Nigeria, were plagued by violent uprisings and civil wars. Among the literary works that tackle the preconditions of the Nigerian Civil War is Chimamanda Ngozi Adichie's Half of a Yellow Sun (2006). Although the novel has been extensively analyzed, the correlation between social identities and conflict eruption almost remains absent. Adopting an interdisciplinary approach, this paper delves into Henri Tajfel's Social Identity Theory and John Turner's Self−Categorization Theory, social psychological theories that examine the interplay of social identity, group identification and social categorization in conflict eruption. The paper aims to show the significant role that social identity, when taken to the extreme, plays in triggering conflict, highlighting the impact of British colonialism in intensifying group identities in Nigeria as presented in Adichie's Half of a Yellow Sun. Moreover, it sheds light on the terrible consequences of conflict escalation.