Southeast Europe
This concept is based on the boundaries of the Balkan peninsula. The countries that have been described as being entirely within the region are: Albania, Kosovo, Bosnia and Herzegovina, Bulgaria, Macedonia and Montenegro.
Balkans Campaign (World War I)
The Balkans Campaign, or Balkan Theatre of World War I was fought between the Central Powers, represented by Austria-Hungary, Bulgaria, Germany and the Ottoman Empire on one side and the Allies, represented by France, Montenegro, Russia, Serbia, and the United Kingdom (and later Romania and Greece, who sided with the Allied Powers) on the other side.