Book excerpt: The topic of this book deals with a highly relevant empirical issue: East asian security and the dynamics of the respective governance structure or architecture are not only of regional but of global concern. Since the pivot of the American pivot to East Asia and other external actor ́s responses to it the security architecture has changed in form, size and function. In order to analyze and explain these changes, hypotheses derived from IR middle range theories (i.e. soft and hard balancing) will be applied to cases of bilateral and multilateral security governance in East Asia.