During Timor-Leste's political and security crisis in 2006, a seemingly latent regional division re-emerged between Timorese from its eastern region, lorosa'e, and those from its western region, loromonu. The conflict between lorosa'e and loromonu revealed critical weaknesses in nation-building. Only four years after independence in 2002, international peacekeeping forces, led by Australia, were redeployed to the new nation-state. This article argues that the enduring political significance of regionalism weakens nation-building in Timor-Leste. This case study revitalises traditional security paradigms by relocating identity-building from the periphery of nation-building to its centre. Identity-building supports the formation of a unifying national political community which transcends social divisions within post-conflict societies.