Coercion and Restraint in the South China Sea: China's Differentiated Assertiveness towards the Philippines and Vietnam

China's behaviour in the South China Sea varies systematically among claimant states rather than unfolding uniformly. It often confronts the Philippines with coercive tactics but adopts greater restraint towards Vietnam. This article explains this patterned variation through a comparative framework that integrates realist and constructivist insights. Drawing on maritime incident data and elite-level interactions, it argues that China calibrates its use of coercion and restraint based on its perception of a claimant's threat-enhancing and affinity-enhancing mechanisms. The Philippines’ alliance with the US and reliance on legal internationalisation of the dispute heighten China's threat perception, driving coercion. By contrast, Vietnam's non-alignment and party-to-party ties foster elite trust and crisis management with China. This encourages restraint despite overlapping claims. The article advances the concept of differentiated assertiveness to capture this conditional and relational logic and situates South China Sea disputes within broader structural and ideational patterns.