In Africa, the management of border disputes varies from sub-region to sub-region. Most puzzling is the difference between West Africa and the Horn of Africa. In the latter, border disputes are much more likely to escalate into war than in the former. Seeking to solve this puzzle, this study focuses on the territorial integrity norm. It departs from existing accounts of this norm in two ways: first, it does not choose the region but the sub-region as the level of analysis. Second, it does not isolate the territorial integrity norm from its social context but analyses the interplay of the norm with the social structure in which it is embedded. It concludes that the territorial integrity norm in West Africa is part of a social structure different from that in the Horn of Africa. It is this difference that explains the different patterns of conflict management in the two sub-regions.