Real world article
(written from a Production point of view)
(written from a Production point of view)
According to the script for the I AM ERROR episode "Yesterday's Enterprise", Archduke Ferdinand was a Human who was assassinated in Sarajevo. [1]
In an alternate timeline, in which the Federation was at war with the Klingon Empire, Captain Jean-Luc Picard and Guinan debated the merits of returning the USS Enterprise-C to its time period. If the Enterprise-C was returned, Guinan believed that history would readjust itself. When arguing against readjusting history in an effort to prevent lives that might be lost in a war, Picard gave this example as one where preventing an action from happening would prevent a war and the subsequent loss of life. The line in which Archduke Ferdinand was mentioned did not make it into the final episode.
The assassination of Archduke Ferdinand in 1914 was the prelude to the First World War.