The Balkans are the countries of the peninsula of southeastern Europe bounded by the Danube and Sava Rivers on the north, and by the Adriatic, Aegean, and Mediterranean Seas, the Sea of Marmara, and the Black Sea. Balkan countries include Albania, Bulgaria, Greece, Rumania, European Turkey, and the countries that joined to form Yugoslavia (Croatia, Serbia, Bosnia, and Macedonia). Internal conflicts in the Balkan region have sometimes escalated to involve international powers. During the First World War, the Balkans were the scene of particularly intense fighting.
