Yemens civil war, in its sixth year as of 2021, has killed more than 250,000 people and created one of the worst humanitarian crises in the world today. It has become a proxy war between the Iranian-supported Houthis, United Arab Emirates-supported southern separatists, and the Saudi-supported internationally recognized government of Yemen. Despite years of United Nations-brokered negotiations, the antagonists have become increasingly entrenched and their positions seemingly irreconcilable. Time and again, negotiated cease-fires have proved unsustainable and once-promising confidence-building measures have failed to change the status quo, let alone achieve an enduring peace. In this report, the authors trace the origins of the conflict, diagnose its costs, identify the underlying drivers of local conflict and mediation mechanisms, and describe how political influence, economic interests, and military ties have shaped the roles of key actors in the peace process. This analysis draws on five years of RAND Corporation research, including an expansive data collection effort in Yemen that assessed national conflict dynamics, regional influence networks, and local drivers of conflict and sources of resiliency, as well as 200 interviews with key military, government, community, and tribal actors across Yemen. This research offers clear recommendations for ending the cycle of violence, failed peace talks, and broken promises. An enduring peace requires a coordinated international approach to security and the formation of an international body with the influence, mission, and resources to support what will be a decades-long process of reconciliation, reconstruction, and redevelopment.