The powder keg of Europe, sometimes alternately known as the Balkan powder keg, refers to the Balkans in the early part of the 20th century preceding World War I. There were a number of overlapping claims to territories and spheres of influence between the major European powers such as the Russian Empire, the Austro-Hungarian Empire, the German Empire and, to a lesser degree, the Ottoman Empire, the United Kingdom and Kingdom of Italy.
In addition to the imperialistic ambitions and interests in this region, there was a growth in nationalism with the indigenous peoples of this region leading to the formation of the independent states of Greece, Serbia, Montenegro, Bulgaria, Romania and Albania.
Within these nations there were movements to create "greater" nations, that is to enlarge the boundaries of the state beyond those areas where the national ethnic group was in the majority (irredentism). This led to conflict between the newly independent nations and the empire from which they split, the Ottoman Empire. Additionally, it led to differences between the Balkan nations who wished to gain territory at the expense of their neighbours. Both the conflict with the Ottoman Empire and between the Balkan nations led to the Balkan Wars in 1912–13.
In a different vein, the ideology of Pan-Slavism in Balkans gained popularity; the movement built around it in the region sought to unite all of the Slavs of the Balkans into one nation, Yugoslavia. This, however, would require the union of several Balkan states and territory which was part of Austria-Hungary. For this reason, Pan-Slavism was strongly opposed by Austria-Hungary, while it was supported by Russia which viewed itself as leader of all Slavic nations.