The Free State of Brunswick (Freistaat Braunschweig) was a state of the German Reich in the time of the Weimar Republic. It was formed after the abolition of the Duchy of Brunswick in the course of the German Revolution of 1918–19. Its capital was Braunschweig (Brunswick).
The Duchy of Brunswick had been established after the 1814 Congress of Vienna, as a sovereign successor state of the German Confederation. It roughly comprised the incoherent territory of the former Principality of Brunswick-Wolfenbüttel, stretching from Holzminden on the Weser River in the west to Blankenburg in the Harz mountain range and Calvörde in the east.
The Brunswick territory was largely surrounded by the Prussian provinces of Hanover (the former Kingdom of Hanover) and Saxony. From 1913 it was ruled by Duke Ernest Augustus of the House of Hanover.
The reports on the Kiel mutiny of 3 November 1918 sparked unrest in Braunschweig, when local revolutionaries led by the Independent Social Democratic Party of Germany (USPD) stormed the local prison, occupied the railway station and the police headquarters, and also attacked Brunswick Palace. On 8 November Duke Ernest Augustus of Brunswick was forced to abdicate and went into exile. Two days later, a workers' council proclaimed the "Socialist Republic of Brunswick", ruled by a council of USPD revolutionaries.
However, their intentions to implement a Soviet republic failed, as in the first parliamentary elections on 22 December 1918 the USPD officials were outnumbered by the Social Democrats (SPD), who reached 27.7% of the votes cast. On 22 February 1919, both parties formed a coalition government led by the USPD politician Joseph ("Sepp") Oerter, that shifted the state's constitution towards a parliamentary republic. However, the government had to deal with subsequent uprisings in the capital Braunschweig, led by the Communist Spartacus League, which on 9 April called a general strike. Four days later, the Reich government declared the state of emergency in Brunswick and crushed the Spartacist revolt with the aid of invading Freikorps troops under Georg Ludwig Rudolf Maercker.