This thesis looks at why it is so difficult to achieve a stable and long-lasting peace in conflicts involving warlords. The theory of self-enforcing agreements is used to answer the research question. The analysis proceeds in three steps. First, the possibility of rendering a warlord incapable of continuing armed conflict by killing him, defeating him militarily, or arresting him, is considered. Second, the focus is on conditions under which threats to suspend or terminate a peace agreement involving a warlord might render the agreement self-enforcing. Finally, the thesis looks at whether external enforcement can be effective in sustaining a peace agreement when a self-enforcing agreement is not possible.