Congress of Berlin
The 1878 great-power conference that redrew the Balkans over the heads of the people living there, and planted most of the grievances that detonated in 1914.
For one month in the summer of 1878, the foreign ministers of Europe sat in Berlin and rearranged the Balkans. Almost nobody from the Balkans was consulted. The settlement they produced kept the peace between the great powers for a generation and guaranteed that the region beneath them would be at war repeatedly, which was a trade the men in the room were content to make.
The problem the Congress was called to fix
Russia had just won a war against the Ottoman Empire, fought partly on the grounds of protecting Balkan Christians and entirely in pursuit of influence over the straits. The peace it imposed at San Stefano in March 1878 created a very large autonomous Bulgaria stretching to the Aegean, obviously destined to be a Russian client, and effectively ended Ottoman power in Europe.
Britain and Austria-Hungary refused to accept it. London would not tolerate Russia near the Mediterranean; Vienna would not tolerate a big Slavic state on its southern flank. Both hinted at war. Otto von Bismarck offered Berlin as neutral ground and himself, in his phrase, as the honest broker, which meant a broker who intended to charge nothing because what he wanted was a Europe too balanced to fight.
The bargain
The Congress ran from mid-June to mid-July 1878, and much of the real business had been fixed in advance in secret bilateral deals.
Bulgaria was cut into three. A shrunken principality north of the Balkan mountains got autonomy; Eastern Rumelia to the south became an autonomous Ottoman province; Macedonia went straight back to Ottoman rule. Serbia, Montenegro, and Romania received full independence, with less territory than any of them wanted. Austria-Hungary was authorized to occupy and administer Bosnia and Herzegovina while the Ottomans kept nominal ownership, an arrangement designed to be permanent and deniable at once. Britain took Cyprus, agreed beforehand in a secret convention with Istanbul. Russia collected southern Bessarabia and territory in the Caucasus, including Kars and Batum, and considered itself robbed.
Every clause a future war
The Congress is a case study in what happens when strategic tidiness overrides local reality.
Russia had won the war and lost the peace, and the humiliation was blamed squarely on Bismarck. The Three Emperors' understanding between Germany, Austria, and Russia never recovered; Bismarck signed a defensive alliance with Austria-Hungary the following year, and the slow sorting of Europe into two armed camps had begun.
Bulgaria never accepted losing Macedonia and spent the next forty years trying to get it, which is the direct road to both Balkan Wars and to Bulgaria fighting on Germany's side in two world wars. Serbia, blocked from expansion westward and denied the Adriatic, turned its ambitions toward Bosnia, where several million South Slavs now lived under Habsburg administration. When Vienna converted its occupation into outright annexation in 1908, it triggered a crisis that nearly caused war and left Serbian nationalists with a permanent cause. Six years later one of them shot the Archduke Franz Ferdinand in Sarajevo.
The Ottoman Christians of Macedonia and Armenia, whose treatment supplied the moral pretext for the whole affair, got paper guarantees of reform and no mechanism to enforce them.
The men in Berlin thought they were preventing a great-power war, and for thirty-six years they were right. The bill arrived in 1914, and it was itemized: Bosnia, Macedonia, Serbian ambition, Russian resentment. Settlements imposed on populations that were never asked do not resolve conflicts. They schedule them.