Austro-Hungarian occupation of Bosnia and Herzegovina

The campaign to establish Austro-Hungarian rule in Bosnia and Herzegovina lasted from 29 July to 20 October 1878 against the local resistance fighters supported by the Ottoman Empire. The Austro-Hungarians entered the country in two large movements: one from the north into Bosnia, and another from the south into Herzegovina. A series of battles in August culminated in the fall of Sarajevo on the 19th after a day of street-to-street fighting. In the hilly countryside a guerrilla campaign continued until the last rebel stronghold fell after their leader was captured.

Following the Russo-Turkish War of 1877–78, the Congress of Berlin was organized by the Great Powers. By article 25 of the resulting Treaty of Berlin (13 July 1878), Bosnia and Herzegovina remained under the sovereignty of the Ottoman Empire, but the Austro-Hungarian Empire was granted the authority to occupy the vilayet (province) of Bosnia and Herzegovina indefinitely, taking on its military defence and civil administration. The Austro-Hungarians also received the right to indefinitely occupy strategic posts in the sanjak of Novi Pazar:

The provinces of Bosnia and Herzegovina shall be occupied and administered by Austria-Hungary. The government of Austria-Hungary, not desiring to undertake the administration of the Sanjak of Novi-Pazar, which extends between Serbia and Montenegro in a South-Easterly direction to the other side of Mitrovitza, the Ottoman administration will continue to exercise its functions there. Nevertheless, in order to assure the maintenance of the new political state of affairs, as well as freedom and security of communications, Austria-Hungary reserves the right of keeping garrisons and having military and commercial roads in the whole of this part of the ancient vilayet of Bosnia. To this end the governments of Austria-Hungary and Turkey reserve to themselves to come to an understanding on the details.

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Wikipedia