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 …