Arming the archipelago: explaining A2/AD divergence in the South China Sea

How do secondary powers develop anti-access/area denial (A2/AD) capabilities when facing asymmetric threats? This article explains variation in maritime defense modernization patterns across Southeast Asian states through a novel framework that distinguishes between anti-access (A2) and area denial (AD) based on operational range, strategic purpose, and integration requirements. We argue that A2/AD development patterns result from the interaction of two variables: the level of external threat states perceive regarding maritime territorial challenges, and the quality of civil-military relations that affects whether external pressures produce coherent or incoherent procurement. Through comparative case studies of Vietnam, the Philippines, Malayasia and Indonesia, we identify four distinct pathways: balanced acceleration, constrained coherence, selective prioritization, and undisciplined accumulation. This framework advances understanding of secondary-state security behavior by moving beyond diplomatic alignment theories to illuminate the domestic institutional factor influencing defense procurement effectiveness, with significant implications for regional deterrence stability in contested maritime regions.