The known members of The Black Hand, which was officially called Ujedinjenje ili Smrt, Union or Death, were Captain Dragutin "Apis" Dimitrijevic and Gavrilo Princip, the assassin of Archduke Franz Ferdinand. The total membership, including many Serbian military officers, is unknown, but it may have amounted to 2,500.
The group was organized into grassroots cells, each containing between three and five members. These were answerable to district committees, which were answerable to the central committee in Belgrade. At the very top of the organization's hierarchy were the 10 members of the executive committee, whose leader was Dimitrijevic.
Of the utmost concern to The Black Hand was the secrecy of its members' identities, especially those higher up in the chain of command. For this reason, it was often the case that members knew only those in their own cell, as well as just one of their superior officers.
The Black Hand were violently in favor of Serbian independence from Austria, and they are best remembered for organizing the assassination of Austrian heir-apparent, Archduke Franz Ferdinand, in 1914. Their actions intensified the already strained Serbian-Austrian relations, and led to the intervention of Western European nations in what ultimately became World War I.
In June of 1917, Dimitrijevic and three of his subordinates were executed by firing squad while three others were given lengthy prison sentences.