This article examines the new norms in bilateral, regional and international relations that evolved in the wake of the emergence of the Eritrean state which had successfully challenged the hegemonic claims of both the imperial and Afro-Marxist Ethiopian state. The analysis proceeds from a retelling of the events in 1998 which precipitated the break between the Ethiopian and Eritrean partners of the old alliance against the Mengistu regime, then examines the structural anomalies in the alliance and their consequences. The evidence examined here suggests that two inter-related phenomena help to shed light on the structural, historical and philosophical underpinnings of the 1998–2000 Ethio–Eritrean conflict: (1) the asymmetry of vision between diasporic and hegemonic states, leading to a clash of interests; (2) the failure of both post-war regimes to formalise their ‘understandings’ into formal treaties based on international law.

As the two countries pursued different systems of economic and political governance, the cluster of informal understandings unravelled amidst conflicting interpretations of issues relating to sovereignty: territorial jurisdiction and citizenship. What emerges is a picture – seen from below rather than from above – of the norms and rules that govern the conduct of interstate relations between Africa's most recent and oldest sovereign states.