The Macedonian Campaign of World War I (October 1915-November 1918) traditionally remains one of the understudied theatres of the historiography of the conflict. Despite its vital importance in the outcome of the war, it is still considered as a mere sideshow compared to the Western Front and the Gallipoli Campaign. This dissertation presents a much-needed re-evaluation of the Macedonian Campaign's diplomatic and political origins within the war's early context. In doing so, this study first concentrates on a longue durée perspective and assesses the main historical events in the Balkans and Central Europe from the end of the French Revolution to World War I. In a perspective running throughout the entire nineteenth century, this dissertation integrates the importance of nascent nationalism in the Balkans and examine the Austro-Hungarian Empire's steady decline and subsequent diplomatic realignment toward the Balkans. Similarly, this work depicts the intense power struggle in Southeastern Europe between some of this story's main protagonists, namely the Austro-Hungarian, Russian and Ottoman Empires. This dissertation also evaluates the rise of new regional powers such as Bulgaria and Serbia and examines their connection to the European balance of power and general diplomatic equilibrium. In the first half of this dissertation, I present an overview of some of the most crucial episodes that paved the way to the onset of World War I and the inception of the Macedonian Campaign: The Russo-Turkish War of 1877-1878, the Congress of Berlin of 1878, The Bosnian Crisis of 1908-1909, the Italo-Ottoman War of 1911-1912, and the Balkan Wars of 1912-1913. In the second part of this study, the main thread of the analysis is the crucial Anglo-French relations that took place between the end of the nineteenth century and World War I. This study describes the importance of Anglo-French relations regarding the Macedonian Campaign's inception and highlights the fragile nature of the Entente Cordiale and some of the fundamental issues that affected the Anglo-French conduct of military operations on the Western Front as well as in the Balkans. Therefore, this study underlines why the Macedonian Campaign, suffered so much from a lack of care, preparation, and a much-needed strategic insight and leadership that could have decisively influenced the campaign and potentially have altered the outcome of an eventually successful Allied endeavor in the Balkans.