Under the leadership of Liebknecht and Luxemburg, the KPD was committed to a violent revolution in Germany, and during 1919 and 1920 attempts to seize control of the government continued. Germany's Social Democratic government, which had come to power after the fall of the Monarchy, was vehemently opposed to the KPD's idea of socialism. With the new regime terrified of a Bolshevik Revolution in Germany, Defense Minister Gustav Noske formed a series of anti-communist paramilitary groups, dubbed "Freikorps", out of demobilized World War I veterans. During the failed so-called Spartacist uprising in Berlin of January 1919, Liebknecht and Luxemburg, who had not initiated the uprising but joined once it had begun, were captured by the Freikorps and murdered. The Party split a few months later into two factions, the KPD and the Communist Workers Party of Germany (KAPD).
Following the assassination of Leo Jogiches, Paul Levi became the KPD leader. Other prominent members included Clara Zetkin, Paul Frölich, Hugo Eberlein, Franz Mehring, August Thalheimer, and Ernst Meyer. Levi led the party away from the policy of immediate revolution, in an effort to win over SPD and USPD voters and trade union officials. These efforts were rewarded when a substantial section of the USPD joined the KPD, making it a mass party for the first time.
Through the 1920s the KPD was racked by internal conflict between more and less radical factions, partly reflecting the power struggles between Zinoviev and Stalin in Moscow. Germany was seen as being of central importance to the struggle for socialism, and the failure of the German revolution was a major setback. Eventually Levi was expelled in 1921 by the Comintern for "indiscipline." Further leadership changes took place in the 1920s. Supporters of the Left or Right Opposition to the Stalin-controlled Comintern leadership were expelled; of these, Heinrich Brandler, August Thalheimer and Paul Frölich set up a splinter Communist Party Opposition.