What is success in war? Who defines success? A review of past theorists such as Sun Tzu, Thucydides, Jomini and Clausewitz along with modern scholars such as William Martel, Azar Gat, and J. Boone Bartholomees produces a model for understanding success. First, success must be defined using political terms. Since war is a political endeavor at the strategic level, success in war must be defined using political language. Politicians and military leaders must define the objectives of war and convince the population that the political condition has improved using whatever political language is required for the given situation. Military tactical language is not sufficient for defining success at the political level. Second, the political leaders must define the desired objective for the military campaign. Political leaders understand politics and the nature of the population. Military leaders should help political leaders define success in war. Politicians understand the population and military leaders understand the theory and history of war. Third, the political condition that exists at the end of the war determines whether the war was successful. Victory in battle is important but is not always necessary for success. War must improve the political condition. Finally, a review of two US conflicts in Lebanon against the success model demonstrates its utility. The political and military leaders in Lebanon 1958 followed the theory of the model and achieved a successful outcome for the conflict. The political and military leaders of Lebanon 1983 did not adhere to the theory of the success model and were unable to achieve success. Although adherence to the model will not ensure future success, it can be used to help political and military leaders better prepare for future conflict.