Since 1997, RAND has studied options for configuring a future Agile Combat Support (ACS) system that would enable Air and Space Expeditionary Force (AEF) goals to be achieved. Operation Enduring Freedom (OEF), in Afghanistan, offered an opportunity to examine the implementation of new ACS concepts in a contingency environment. In 2000, Project AIR FORCE helped evaluate combat support lessons from Joint Task Force Noble Anvil (JTF NA), the U.S. component of Operation Allied Force (OAF), in Serbia. [Joint Task Force Noble Anvil was the organization overseeing U.S. forces involved in OAF. This report concentrates on Air Force operations conducted by Joint Task Force Noble Anvil.] Some of the concepts and lessons learned from JTF NA were implemented in supporting OEF. Supporting Air and Space Expeditionary Forces: Lessons from Operation Enduring Freedom presents an analysis of combat support experiences associated with Operation Enduring Freedom and compares these experiences with those associated with Operation Allied Force The analysis offered an opportunity to compare findings and implications from JTF NA and OEF. Its objectives were to indicate the performance of combat support in OEF, examine how ACS concepts were implemented in OEF, and compare JTF NA and OEF experiences to determine similarities and applicability of lessons across experiences and to determine whether some experiences are unique to particular scenarios. This analysis concentrates on U.S. Air Force operations in support of OAF--specifically, Joint Task Force Noble Anvil and the first 100 days of OEF. The report focuses on experiences from OEF and what those experiences imply for a combat support system designed to ensure that AEF goals can be achieved. It does not address other portions of the War on Terrorism, such as Homeland Defense (for example, Operation Noble Eagle). Both JTF NA and OEF illustrate, among other things, that more attention should be focused on political agreements and engagement policies required to develop forward operating locations. As well, in many cases in JTF NA and OEF, the current resource-usage factors are more demanding than the assumptions used to fund resources--an imbalance that creates resource shortages that occur in contingency operations. Task Force Enduring Look (AF/CVAX) sponsored this research, which was conducted in the Resource Management Program of Project AIR FORCE, in coordination with the Air Force Deputy Chief of Staff for Installations and Logistics (AF/IL) and the Air Force Deputy Chief of Staff for Air and Space Operations (AF/XO). The research for this report was completed in February 2003. This report should be of interest to logisticians, operators, and mobility planners throughout the Department of Defense, especially those in the Air Force.