A Theory of Hegemonic Decline and Regional Order Transformation in West Africa: Nigeria’s Diminishing Leadership Capacity

This dissertation develops an original theory of hegemonic decline and regional order transformation in West Africa, using the case of Nigeria's diminishing regional leadership capacity from the 1990s to the 2020s as the primary empirical foundation. Nigeria's claim to West African hegemony, grounded in its demographic weight, military capacity, and economic size, faces mounting internal and external challenges that the existing regional hegemony and power transition literature has not adequately theorised in the African context. The dissertation proposes the African Hegemonic Erosion Theory, which identifies five pathways through which hegemonic capacity erodes in the African regional order context: domestic security overstretch, economic stagnation relative to regional expectations, legitimacy deficit accumulation, external power penetration, and sub-regional coalition formation against the hegemon. A three-phase mixed-methods design is employed: a longitudinal power index analysis measuring Nigeria's relative capabilities across 11 West African states from 1990 to 2023; comparative case analysis of six critical West African governance crises in which Nigerian leadership was tested; and 65 elite interviews with West African diplomats, ECOWAS officials, and international relations scholars. Power Transition Theory, Hegemonic Stability Theory, and the Regional Security Complex Framework provide the theoretical anchors. Empirical findings confirm a secular decline in Nigeria's effective regional leadership capacity since approximately 2010. Keywords: hegemonic decline, West Africa, regional order, Nigeria, power transition.