A large literature has emerged in political science that studies the wars in Afghanistan and Iraq. This article summarizes the lessons learned from this literature, both theoretical and practical. To put this emerging knowledge base into perspective, we review findings along two dimensions of conflict: factors influencing whether states or substate groups enter into conflict in the first place and variables affecting the intensity of fighting at particular times and places once war has started. We then discuss the external validity issues entailed in learning about contemporary wars and insurgencies from research focused on the Afghanistan and Iraq wars during the period of US involvement. We close by summarizing the uniquely rich qualitative and quantitative data on these wars (both publicly available and what likely exists but has not been released) and outline potential avenues for future research.