Out of Austria, in addition to Dalmatia, three new countries form: The Principality of Slovenia (March 1918), the Banate of Croatia (December 1917) and the Kingdom of Serbia (December 1917). Serbia and Croatia fight a brief battle which leads to Serbia acquiring lands as far as Brčko.
Croatia and Slovenia form a union called the Slavonic Union, in October 1918, in which both are more or less equal partners. Serbia, after some convincing, joins the Slavonic Union in December 1918. With Turkey still a threat in the south and the proposition of a confederation based on the principle of equality of nations appealing, Bulgaria joins the Slavonic Union in January of 1919. Dalmatia is persuaded to join the Slavonic Union too (we're stronger if we're all together, but if you don't join we'll attack you). Dalmatia realises that they are numerous enough to be a loud voice in the Union, so they formally join on 27 March 1919. That same day the Slavonic Union is renamed the Danubian Confederation. Its territory covers what is now Dalmatia, Croatia, Serbia, Sanjak and Bulgaria.
After the defeat of the Bolsheviks, several leading Bolshevik figures came to Danubia (Zinovyev, Bukharin, Lenin - in Dalmatian orthography Zinoviev, Buharin, Lenyin). They became important figures in the Communist Party of the Danubian Confederation (CPDC).
Dalmatia had good relations with Italy and France since the beginning of the 20th century, and very bad with Austria, these policies were continued by Danubia, so in GW2 they fought against Austria and Germany (and Greece, since the Bulgarians wanted southern Macedonia). The Danubian Confederation fought against the Grossartige Allianz during the Second Great War, until the civil war broke out.
In 1944 a civil war began in the Danubian Confederation after the Communists revolted against the ruling monarchists. Interestingly the war did not divide on ethnic lines, but on political views instead. During this time a young Danubian (he was half Slovene and half Croat) named Josip Broz came to the forefront of the CPDC after proving himself to be a brilliant tactician. The Communists won the civil war and on 19 July 1947 the Confederation of Soviet Danubian States (CSDS) was proclaimed. Broz became head of state with the aging but still lucid Lenin becoming General Secretary. Zinovyev became foreign minister, Bukharin became minister of home affairs.
The CSDS was a strong regional power throughout its existence and played some role on the world stage. It was an important player when it came to African affairs since it maintained close relations with the former Austro-Dalmatian colonies there (Mali, Togoland, Kamerun, Austrian Kongo etc.), all of which still have Dalmatian as an official language.
The policy of the communists was Brotherhood and Unity (an enforced friendship of nations that superficially worked, but underneath the shiny veneer, the ancient ethnic rivalries were still buried) and modernisation.
One by one the old Communists died off. Lenin was the first, followed by Bukharin and then Zinovyev. Broz died in 1981. After Broz's death the CSDS began to weaken internally, but few at the time would have predicted its complete collapse into civil war in 1988.
