The military has an important role in peace and development work. Having skilled, experienced and knowledgeable personnel on peace-promoting missions abroad is crucial to ensure the missions success. A consequence of attrition is that military organizations lose valuable skills, experiences and qualities of service members. Preventing attrition is essential to maintain readiness, morale and knowledge. It also has a positive impact on peacekeeping missions, humanitarian relief and interactions with civil society. Current research on attrition has focused on early attrition; separation that occurs before a full term of service. It has focused on pre-enlistment factors of individuals that would make them less suitable to remain in the military. Current research has looked at attrition among all branches of the United States military. The focus of this thesis is to identify the main reasons for attrition among enlisted United States Marines. Focus is on the effect dissatisfaction of service and civilian opportunities has on attrition. It will also identify areas in need of improvement to prevent attrition. This research is a qualitative field study taken with an abductive approach. The main method of data collection was in-depth semi-structured interviews with active and retired U.S Marines, on site in North Carolina. The theory used to analyze the results is the Rational Choice-Theory, an individualistic theory that focus on individual’s actions and the values and beliefs shaping the action. Dissatisfaction because of bad leadership, military structures, long days of work and lack of motivation affected attrition. Civilian opportunities such as college and spending more time with family also played a part in the decision-making regarding reenlistment. Among the Marines, dissatisfaction arising from long-term issues was the factor that affected attrition the most. Civilian opportunities were in some cases the last pull needed to leave service. The findings can assist in making changes that will have a positive effect on the Marines. It can encourage Marines to pursue a longer military career, and hence keep valuable skills and experiences. These Marines can then continue to do important work within the peace and development field.