On 8 October 1912 (25 September, by the Julian calendar then still in use in Russia and elsewhere), Montenegro's ambassador to Istanbul handed his country's declaration of war to the Ottoman Foreign Minister. The note said:
"Your excellency, I feel sorry to inform that Montenegro Kingdom government has used up all the friendly efforts to solve the continuous disagreements with the Ottoman government. With the permission of my King his majesty Nikola the First, I am honored to inform your excellency that as for today, Montenegro government breaks off all the relations with the Ottoman government and both Montenegrins and their brothers under the reign of Ottoman empire intrust Montenegrin weapons in making the Ottomans legitimatize their rights that have been ignored for centuries.
8 October/25 September 1912 Plamenatz”
In the meantime, King Nicola of Montenegro called the Ottoman ambassador to his palace and, after a 45 minute conversation, made a declaration of war and told the ambassador that he and his staff were to be escorted the border.
During the summer of 1912 there had already been clashes between Montenegrin and Ottoman forces in the vicinity of Montenegro's border with Ottoman-ruled Albania. Albanian nationalists were seeking independence from Ottoman rule and Montenegro had territorial ambitions of its own in the area.
The declaration of war by the King of Montenegro and his ambassador in Constantinople marked the official start of the First Balkan War, which was to bring Europe to the brink of general war.
Montenegro was one of the weakest of the Balkan states, but it was acting as a stalking-horse for more powerful Balkan nations. Bulgaria, Greece and Serbia were linked through the Balkan League, a loose anti-Ottoman (and to some extent anti-Austrian) grouping built on a series of partly secret agreements reached through the course of 1912. Secret talks between Bulgaria and Montenegro in June 1912 had led to a verbal agreement of mutual support against the Ottomans . The system of alliances was completed at the end of September 1912, when Serbia and Montenegro reached an agreement providing for mutual military assistance against the Ottomans.
Russian mediation had helped the construction of the Balkan League. Russia saw the League as a potential counter to the influence of Austria-Hungary and Germany in the region. However, the Balkan states seem not to have shared their war plans with Russia. In the summer and autumn of 1912, Russia was anxiously seeking intelligence on the issue. On 15 September, the Russian military attache in Montenegro, Colonel Potopov reported to headquarters in Russia that the Balkan plan was that "military activities against Turkey should be started by the Allies simultaneously within five days of the ratification of the agreement." 
Montenegrin forces began their offensive the day after Montenegro declared war, with King Nikola's son Peter firing the first shot across the frontier.
- Montenegro in the First Balkan War, , Annals of the Academy of Romanian Scientists , Volume 5, Issue 1/2013, (2013)
- The Montenegrin Policy of Expansion towards Albania before the Balkan War and the 1912 Summer Campaign, , Uluslararası Iliskiler, Volume 6, (2009)
- Crossroads of European Histories, , (2006)