Since the Treaty of Versailles, the Austro-Hungarian Empire had been tearing itself apart over the issue of nationhood. Ruling elites wished to centralise all power in a nationless Emperor, proclaiming theirs to be the Greater Habsburg Empire, which stretched from the Adriatic to the Black Sea, and whose legitimacy was ordained by God. Prominent intellectuals within Austria-Hungary pushed for either reform or revolution, and though in many flavours, this always took the shape of a federal state in which all nations within it would be free, sovereign and united. Finally, the majority of minority populations within Austria-Hungary wished to secede from the Empire and form their own nation-state. It was this latter current that spilled the goblet on February 3rd, 1920, when Hungarian trade unions took to the streets and declared their independence as the Hungarian Soviet Republic, obviously inspired by the raging success of the Russian Bolsheviks. K.u.K. units sent to quell the uprising found themselves facing tens of thousands of Hungarian deserters, veterans and mobilised working class citizens.
But this was only the beginning. On March 19th, unable to obtain enough revenue to pay its war bonds and loans used to fight World War I, the Austro-Hungarian throne chose to print money as fast as possible. Hyperinflation caused food prices to soar and soldiers' wages to become worthless. Dozens of rebellions became hundreds, and this vast realm of land from the Alps to the coast of Moldavia became filled with rebels, mutinying soldiers and rioting workers. Thus began the Austro-Hungarian Civil War.
Imperial forces were taken by surprise on June 24th, the sixth anniversary of Archduke Franz Ferdinand's assassination, when supporters of the Imperial Federal Party stormed Hofburg Palace. Here, Emperor Charles I was forced to abdicate. Through radio and lightning-fast newspaper prints it was proclaimed that a new Danubian Federation would emerge from Vienna, now with Queen Sophie I at its throne, only daughter of the Archduke whose life project had been a similar confederation. Soon after, the Danubian Constitution of 1920 was published far and wide.
Over four years of harsh fighting followed. This is meant in all senses, as the IFP's liberal policies allowed the Empire's multinational intelligentsia to fight in all fields of science and the arts, trying to decide what the future of the Federation was, while its soldiers battled absolutists, communists and secessionists on all fronts. One major achievement was the creation of Standard Danubian, an artificial language based on the Bavarian dialect, but which was designed to be easily learned by Czech, Slovakian, Polish, Romanian, Hungarian, Serbo-Croatian, Slovenian and Ukrainian speakers, though it was unintelligible to German ones. The Imperial Federal Party wasted no time in implementing this language across schools in the regions it controlled, turning it into the language of government by the year 1928.
By mid-1924, Vienna was exhausted. All remaining participants convened in said city to discuss peace, with the following result.
- Romania would regain its independence, reinstating Ferdinand I as king.
- Galicia would become part of the Kingdom of Ukraine, also known as Yurislanzia.
- Serbia, Bosnia, Croatia, Montenegro, Albania and Slovenia would secede from the Empire, forming an allied bloc of monarchies.
- All political paramilitaries within the remaining Habsburg territory were to disarm and surrender.
- The Habsburg realm would be permanently reorganised into the Danubian Federation, consisting of Austria, Czechia, Slovakia, Hungary and Transylvania as equal democratic states. Only the title of King or Queen of Danubia would hold any political weight, as all public servants would be chosen by merit or election.
On the 23rd of September 1924, the Austro-Hungarian Civil War came to an end as this Treaty of Vienna was signed by all attending parties.