The Bulgarian principality won a war against Serbia and incorporated the semi-autonomous Ottoman territory of Eastern Rumelia in 1885, proclaiming itself an independent state on 5 October 1908. In the years following independence, Bulgaria increasingly militarized and was often referred to as "the Balkan Prussia". It became involved in three consecutive conflicts between 1912 and 1918—two Balkan Wars and World War I. After a disastrous defeat in the Second Balkan War, Bulgaria again found itself fighting on the losing side as a result of its alliance with the Central Powers in World War I. Despite fielding more than a quarter of its population in a 1,200,000-strong army and achieving several decisive victories at Doiran and Monastir, the country capitulated in 1918. The war resulted in significant territorial losses and a total of 87,500 soldiers killed. More than 253,000 refugees from the lost territories immigrated to Bulgaria from 1912 to 1929, placing additional strain on the already ruined national economy.