Serbia had gained its independence from the Ottoman Empire in the 19th century, and there was a growing movement among Serbs to unite all Serbs into a single state, including those living in Bosnia and Herzegovina, which were provinces of Austria-Hungary. The assassination of Archduke Franz Ferdinand by a Serbian nationalist was seen as a direct threat to the Austro-Hungarian Empire, and Austria-Hungary issued an ultimatum to Serbia that was intentionally designed to be unacceptable. When Serbia did not fully comply with the ultimatum, Austria-Hungary declared war on Serbia, which led to the outbreak of World War I.