August-October, 1853
With mobilizations underway in both Russia and the Ottoman Empire, both sides begin to think of strategy and where to strike first. Clearly, the Ottoman territories in the Balkans are under direct threat from the encroaching Russian forces north of the Danube, as well as the internal unrest among the Serbs and other Slavs. With exhaustion and frustration there running high, Serbia had largely been forced to disengage from the Bosnian revolt, which had contributed significantly to its collapse and dissipation. Though the rebellion in Bosnia had slowly wound down after grinding on for almost four years, an expanded conflict might boil tensions over again, especially if Russia lends support.
In Serbia, Garašanin's carefully-hatched plans for Serbian self-determination are threatened by the diplomatic trajectory towards inevitable conflict. Potentially joining with Russia in the fight would once again signal that Serbia is not ready to stand on her own, and would at the same time destroy the progress he has made towards building a more permanent relationship between Serbia and France. At the same time, even if France's presumed pact with the Porte is merely a union of convenience, a conflict with those two nations on the same side would likely not benefit Serbia in any way. Thus it would appear there is little reason to Serbia to get involved, and dangerous neutrality is almost as fruitless as impetuously picking the wrong side. Frustrated, Garašanin realizes the window for a settlement in Bosnia is now well and truly closed, and will have to be re-evaluated after the conflict runs its course and is resolved, barring some monumental collapse by Ottoman forces.
As frustrated as the Porte has been with Serbian meddling, the sultan's ministers equally seem to recognize that Serbia is likely to avoid getting involved in the conflict as it currently stands, and thus are counting on Serbian neutrality. Therefore, much of the military resources already in the area can be used to open a front in Wallachia to dislodge the Russian occupation. Omar Pasha, whose forces had fought in Bosnia and Montenegro and hardened themselves against the stalemate of guerrilla war, even now mobilizes his men to move against the enemy now stationed just across the Danube.
The other major Russian-Ottoman frontier, the Caucasus, has been the subject of much more Russian than Ottoman attention in recent decades, as the fiercely independent people of the mountains had proven quite resistant to attempted conquest and occupation. Though war has yet to be officially declared, as early as August skirmishes along this vast and undefined frontier are already underway, and localized attempts to persuade individual peoples or leaders to disrupt the other side's infrastructure or troop movements away from the border indicate a fight that will be filled with disingenuous maneuvering on both sides. In particular, the Ottomans are able to stir up the rebels of Dagestan and Circassia under Imam Shamil, whose Caucausian Imamate has frustrated Russian forces for years. They begin to campaign anew with restored vigor and Ottoman prompting, descending from the mountains and advancing well into Russian Georgia.
The other frontier that the upcoming war will create is the Black Sea, already a flashpoint between the two powers for decades. One unchanging metric in this fight is the numerical superiority of the Russian fleet over its Ottoman counterpart. Since the occupation of the Principalities, Russian ships grow ever bolder in their encroachment upon trade between Istanbul and ports further to the east, despite the presence of French ships in the area intended to act as a deterrent. To avoid complete disaster, the sultan even briefly considers pulling his military vessels back to the Bosporus to avoid a pitched confrontation or an ambush at Russian hands, but it is decided that ceding the entirety of the sea outright would be disastrous for Black Sea ports like Sinop and Trabzon.
With provocations throughout the summer sailing back and forth between the Porte and the tsar like salvoes of a gun, finally one side must bite the bullet and fire off the final word. On October 5, 1853, it is Sultan Abdülmecid who declares war on the Russian Empire, assured that France will soon follow his lead. The Eastern War had begun.