The purpose of this paper is to employ an historical analysis of a campaign as a case study in order to examine the utility of military theory as a guide to decision making and campaign planning. Specifically, the paper uses the Normandy Campaign to explore the usefulness of two theoretical concepts -- the Clausewitzian idea of centers of gravity, and the Jominian theory of lines of operations. While it treats the entire campaign, the analysis focuses in detail upon the campaign plans of both sides, and the major operation which led to the Allied breakout from Normandy and the defeat of the German army in France. After an introduction the paper traces in detail the development and design of the campaign plans of both sides, concentrating especially on the terrain-oriented goals of the Allies and the force-oriented objectives of the Germans. The analysis also examines the differing outlooks that the two major Allies brought to their planning process, and the division within the German high command regarding the most efficacious methods of defense. This section further traces the constraints limiting the freedom of action of the combatants. Having introduced the reader to the campaign, the paper then goes on to define the two concepts that the paper will analyze. Because Chapter One in Epstein's book covers lines of operations in some detail and omits a discussion of centers of gravity, this paper must spend a significant amount of time defining the Clausewitzian term. Following each definition, the paper applies theory to historical experience by identifying the centers of gravity and lines of operation for both sides in the campaign. The paper then narrates and analyzes the campaign in light of the two concepts. It does this by identifying and recounting the events of what it identifies as the three major operations of the campaign -- the landing, the expansion of the foothold, and the breakout. This section attempts to draw the readers attention to missed the oppo