Austria-Hungary — the Dual Monarchy of the House of Habsburg, ruling some fifty-one million people of a dozen nationalities across Central Europe — dissolved in the autumn of 1918 as defeat in the First World War shattered the bargain that held it together. In a matter of weeks its constituent peoples declared their own states: Czechoslovakia on 28 October 1918, the South Slavs the next day, while Hungary severed its union with Austria at the end of October. The last emperor, Charles I, renounced participation in the affairs of state in Austria on 11 November and in Hungary on 13 November 1918, and the empire ceased to exist without ever being formally abolished by treaty in a single act.
What collapsed was not a nation-state but a dynastic federation of nations that had never possessed a common identity. Created by the Compromise (Ausgleich) of 1867, which split sovereignty between an Austrian and a Hungarian half under one Habsburg ruler, Austria-Hungary contained Germans, Hungarians, Czechs, Slovaks, Poles, Ruthenians (Ukrainians), Romanians, Slovenes, Croats, Serbs, Italians, and others. No single people formed a majority. The structure functioned as long as the dynasty, the army, and the bureaucracy could hold its peoples above their national aspirations; war stripped away that capacity.
The empire had triggered the war it could not survive. Its declaration against Serbia in July 1914, after the assassination of Archduke Franz Ferdinand at Sarajevo on 28 June, set the alliances in motion. Four years of total war then exhausted the Monarchy from within: a catastrophic food crisis and famine through the winters of 1917–1918, military exhaustion, and the steady erosion of the central authority that alone bound the nationalities together. As defeat became certain, the peoples for whom the empire had been a compromise rather than a homeland reached for the exit.
The end came as a cascade. President Wilson’s principle of national self-determination gave the subject nations a programme and Allied sympathy; the army disintegrated as conscripts deserted; and the emperor’s last-minute offer to federalize the empire on 16 October 1918 came too late to be anything but its epitaph. By mid-November the Dual Monarchy had broken into the successor states — Austria, Hungary, Czechoslovakia, the new South Slav kingdom, a reborn Poland, and enlarged Romania and Italy — whose borders the peace treaties of 1919–1920 would confirm.
Between 1991 and 1992 the Socialist Federal Republic of Yugoslavia — a federation of six republics in the western Balkans, founded by Josip Broz Tito after the Second World War — broke apart into a series of wars driven by competing nationalisms. Slovenia and Croatia declared independence on 25 June 1991; Macedonia and then Bosnia and Herzegovina followed; and the federation that had bound South Slavic peoples into a single state for nearly half a century dissolved. The wars that accompanied the breakup killed an estimated 130,000 to 140,000 people, displaced millions, and produced the worst atrocities in Europe since 1945, including the siege of Sarajevo and the genocide at Srebrenica.
Yugoslavia did not collapse from invasion or economic ruin alone, but from the deliberate political mobilization of ethnic nationalism in a federation whose unity had depended on a balance that its leaders chose to break. Tito, who had held the country together through personal authority and a carefully engineered system of inter-republican balance, died in 1980. The decade that followed brought economic crisis, the erosion of the federal institutions that had managed ethnic difference, and the rise of nationalist politicians — most consequentially Slobodan Milošević in Serbia — who built power by stoking grievance and fear among their own ethnic groups at the expense of the others.
The mechanism of the dissolution was the conversion of a multi-ethnic federation into a contest over which peoples would control which territory. As republics moved toward independence, the question of the borders — and of the large ethnic minorities stranded on the wrong side of them, especially Serbs in Croatia and Bosnia — turned political rupture into armed conflict. The wars were not spontaneous eruptions of ancient hatred but were organized: armies were mobilized, paramilitaries armed, populations expelled, and the term “ethnic cleansing” entered the world’s vocabulary to describe the systematic removal of communities from contested land.
The human cost fell hardest on civilians. The capital of Bosnia, Sarajevo, endured the longest siege of a city in modern warfare — nearly four years, from April 1992 to February 1996 — under bombardment and sniper fire that killed thousands of its inhabitants. In July 1995, Bosnian Serb forces overran the UN-declared “safe area” of Srebrenica and murdered more than 8,000 Bosniak men and boys in the only act on European soil since the Second World War to be judged a genocide by international courts. What dissolved in 1991–92 was a country; what it left behind was a register of atrocity that the successor states and the wider world are still reckoning with.