the kingdom of serbia () was a country in the balkans which was created when the ruler of the principality of serbia, milan i, was proclaimed king in 1882. it collapsed in 1918 and merged with slovenia,croatia,bosnia,and montenegro into the kingdom of serbs, croats and slovenes or better known as the kingdom of yugoslavia after the austro-hungarian empire collapsed in 1918 along with the german empire while the ottoman empire collapsed in 1923 after world war 1 .