In preparation for the peace conference that was expected to follow World War I, in the spring of 1917 the British Foreign Office established a special section responsible for preparing background information for use by British delegates to the conference. Macedonia is Number 21 in a series of more than 160 studies produced by the section, most of which were published after the conclusion of the 1919 Paris Peace Conference. The study begins by noting that the “area defined by the term Macedonia has varied greatly at different periods, and has at no time formed a single administrative unit.” For the purposes of this study, Macedonia is defined as a 64,745-square kilometer region, formerly ruled by Ottoman Turkey, but by World War I divided among Serbia, Greece, and Bulgaria. The book traces the turbulent history of the country from the time of Philip of Macedon and his son Alexander the Great, through rule by Romans, Bulgarians, Greeks, and Ottomans, up to the Second Balkan War of 1912−13. The book includes sections on physical and political geography, political history, and economic conditions. Social and political conditions are not covered, but are addressed in the volumes in the series devoted to Serbia, Greece, and Bulgaria (Numbers 20, 18, and 22). The study defines the main population groups as Turks, Greeks, Vlachs (mostly Romanians), Albanians, and Serbs. The section on the economy notes that tobacco was by far the most important export, with Austria-Hungary, the United States, and Italy being the main markets. Opium was also a very important (legal) export, as shown in Table I of the appendix.