What drives neighboring states to intervene in the Afghan conflict? This book challenges mainstream analyses which place Afghanistan at the center - the so-called 'heart' - of a large pan- Asian region whose fate is predicated on Afghan stability. Instead Harpviken and Tadjbakhsh situate Afghanistan on the margins of three regional security complexes - those of South Asia, Central Asia, and the Persian Gulf - each characterized by deep security rivalries, which, in turn, informs their engagement in Afghanistan. Within Central Asia, security cooperation is hampered by competition for regional supremacy and great power support, a dynamic reflected in these states' half-hearted role in Afghanistan. In the Persian Gulf, Iran and Saudi Arabia fight for economic and political influence, mirrored in their Afghan engagements; while long-standing Indo-Pakistani rivalries are perennially played out in Afghanistan. Based on a careful reading of the recent political and economic history of the region, and of Great Power rivalry beyond it, the authors explain why efforts to build a comprehensive Afghanistan-centric regional security order have failed, and what might be done to reset inter-state relations.