National security requires a whole-of-government approach. Americans deserve to have all parts of their government working in concert to provide for their common defense and general welfare. How does a leader from one agency lead resources from other departments, nongovernmental organizations, or other nations?Leaders who operate in this joint, interagency, intergovernmental, and multinational environment (JIIM) invariably discover that successful leadership in this environment requires a skillset and knowledge that is somewhat different than what they learned from their agency.The Simons Center for the Study of Interagency Cooperation and the Command and General Staff College Foundation are pleased to bring this publication to the professional discourse. We hope that you find this practitioner’s handbook for leading in the JIIM a useful reference that provides you information to better understand why and how the environment is different than what you know in your agency and that you find useful the information and techniques offered. This is a paperback copy.