The military operations in Iraq and Afghanistan have been the United States' longest military engagements since the Vietnam War and the most severe test of the all-volunteer force, with the possible exception of the Gulf War in 1991. More than 1.5 million service members were deployed between 2002 and 2007, many of them more than once, and the fast pace of deployment has been felt throughout the military. Soldiers and marines have faced a steady cycle of predeployment training and exercises, deployment itself, and postdeployment reassignment and unit regeneration. Service members not on deployment are nonetheless busy planning and supporting military operations, caring for injured service members, and attending to recruiting, training, and other responsibilities at home and abroad. Many service members are married, and deployments have disrupted their family routines and created stress from separation and reintegration. At the same time, the long hours, tension, uncertainty, and violence of deployments have stressed the service members sent to fight. Remarkably, despite the pressures from deployments on service members and their families, reenlistment rates have been stable since 2002. The purpose of this monograph is to enhance understanding of whether deployments affected service members' willingness to stay in the military, as the stress caused by deployments would suggest, and how it was that reenlistment held steady.