Fearing Russian expansionism, Romania secretly joined the Triple Alliance of Germany, Austria-Hungary, and Italy in 1883, but public opinion remained hostile to Austria-Hungary. Romania seized Southern Dobruja from Bulgaria in the Second Balkan War in 1913. German and Austrian-Hungarian diplomacy supported Bulgaria during the war, bringing about a rapprochement between Romania and the Triple Entente of France, Russia and the United Kingdom. The country remained neutral when World War I broke out in 1914, but Prime Minister Ion I. C. Brătianu started negotiations with the Entente Powers. After they promised Austrian-Hungarian territories with a majority of ethnic Romanian population to Romania in the Treaty of Bucharest, Romania entered the war against the Central Powers in 1916. The German and Austrian-Hungarian troops defeated the Romanian army and occupied three-quarters of the country by early 1917. After the October Revolution turned Russia from an ally into an enemy, Romania was forced to sign a harsh peace treaty with the Central Powers in May 1918, but the collapse of Russia also enabled the union of Bessarabia with Romania. King Ferdinand again mobilised the Romanian army on behalf of the Entente Powers a day before Germany capitulated on 11 November 1918.