Chen examines China's unwavering foreign policy toward North Korea, Taiwan, and Mongolia, challenging conventional international relations theory. He introduces ‘buffer thinking’—a geopolitical mentality driving China to secure peripheral territories against potential rivals regardless of global power shifts. Drawing from extensive historical evidence spanning decades, this book demonstrates how buffer thinking functions as an intervening variable that mediates the effects of systemic polarity changes on state behavior. The analysis reveals how this defensive mindset—synthesizing geographical sensitivity, threat perception, and traumatic historical memories—creates a security perimeter extending beyond China's borders. By blending realist perspectives with constructivist insights, it offers a nuanced theoretical framework explaining why China's behavior toward these three states remains ‘territorially conditional.’This is essential reading for international relations scholars and students of geopolitics seeking fresh analytical approaches to buffer state dynamics. It is also a valuable resource for policymakers and diplomats engaged with East Asian security issues who need insights into China's strategic calculations in contemporary great power competition.