Black Hand
The Unification of Death, also known as the Black Hand, was a secret military society of Serbian nationalists. It was formed May 9, 1911 by Serbian army officers aiming to unite all terrorities dominated by South Slavs.

Six of its assassins, including Gavrilo Princip, assassinated Austro-Hungarian royalty Archduke Franz Ferdinand in an attempt to free Serbia of Austria-Hungary. Austria-Hungary immediately declared war and invaded the Kingdom of Serbia, beginning World War I.