They contributed to World War 1 through the assassination of Archduke Franz Ferdinand. The Black Hand was part of a Pan-Slavist movement in which they wanted to unite territories of South Slave that had been annexed by Austria-Hungry. Hopefully this helps.
The Black Hand contributed to World War I by assassinating Archduke Franz Ferdinand of Austria in June 1914, aiming to challenge Austro-Hungarian rule over Slavic territories. This act set off a chain reaction of alliances and conflicts that ultimately led to the war. Their actions underscored the fervent nationalism that characterized the period.
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