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. Rumania is Number 23 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 book includes sections on physical and political geography, political history, social and political conditions, and economic conditions. Long under the control of the Ottoman Empire, Romania declared its independence on May 21, 1877. The Great Powers recognized Romania’s independence at the Congress of Berlin in 1878. Romania concluded a secret defensive alliance with Austria-Hungary in 1883, but it changed its allegiance during World War I and in August 1916 entered the war on the side of Russia. The country was at this time a constitutional monarchy, ruled by King Carol I, in which the Orthodox Church was the official state religion. A note appended to the section on political history deals with international treaties governing navigation on the Danube River, which empties into the Black Sea from Romania. The section on economics notes the growing importance of the petroleum industry in the decade before World War I, as the production of crude oil increased from 493,000 metric tons in 1904 to 1,847,000 metric tons in 1913.