RAND conducted a lessons learned examination of operations analysis, modeling, and simulation in support of Operation Enduring Freedom and Operation Iraqi Freedom. This report identifies ways in which analysts have attempted to support commanders' decisions in counterinsurgency and irregular warfare, describes many of the models and tools they employed, provides insight into the challenges they faced, and suggests ways in which the application of modeling, simulation, and analysis might be improved for current and future operations. RAND identified four broad categories of decisions: force protection, logistics, campaign assessment, and force structuring. Modeling, simulation, and analysis were most effective in supporting force protection and logistics decisions, and least effective in supporting campaign assessment and force structuring.