Rosa Luxemburg in the context of "Russian Revolution of 1905"

The Communist Party of Germany (German: Kommunistische Partei Deutschlands, pronounced [kɔmuˈnɪstɪʃə paʁˈtaɪ ˈdɔʏtʃlants] ; KPD [ˌkaːpeːˈdeː] ) was the major far-left political party in the Weimar Republic during the interwar period, an underground resistance movement in Nazi Germany, and a minor party in Allied-occupied Germany and West Germany during the post-war period until it merged with the SPD in the Soviet occupation zone in 1946 and was banned by the West German Federal Constitutional Court in 1956.

The construction of the KPD began in the aftermath of the First World War by Rosa Luxemburg's and Karl Liebknecht's faction of the Independent Social Democratic Party of Germany (USPD) who had opposed the war and the Majority Social Democratic Party of Germany (MSPD)'s support of it.

Trotskyism (Russian: Троцкизм, Trotskizm) is the political ideology and branch of Marxism and Leninism developed by Russian revolutionary and intellectual Leon Trotsky along with some other members of the Left Opposition and the Fourth International. Trotsky described himself as an orthodox Marxist, a revolutionary Marxist, and a Bolshevik–Leninist as well as a follower of Karl Marx, Friedrich Engels, Vladimir Lenin, Karl Liebknecht, and Rosa Luxemburg. His relations with Lenin have been a source of intense historical debate. However, on balance, scholarly opinion among a range of prominent historians and political scientists such as E. H. Carr, Isaac Deutscher, Moshe Lewin, Ronald Suny, Richard B. Day and W. Bruce Lincoln was that Lenin's desired "heir" would have been a collective responsibility in which Trotsky was placed in "an important role and within which Stalin would be dramatically demoted (if not removed)".

Trotsky advocated for a decentralized form of economic planning, workers' control of production, elected representation of Soviet socialist parties, mass soviet democratization,the tactic of a united front against far-right parties,cultural autonomy for artistic movements, voluntary collectivisation, a transitional program, and socialist internationalism. He supported founding a vanguard party of the proletariat, and a dictatorship of the proletariat (as opposed to the "dictatorship of the bourgeoisie", which Marxists argue is a major component of capitalism) based on working-class self-emancipation and council democracy. Trotsky also adhered to scientific socialism and viewed this as a conscious expression of historical processes. Trotskyists are critical of Stalinism as they oppose Stalin's theory of socialism in one country in favour of Trotsky's theory of permanent revolution. Trotskyists criticize the bureaucracy and anti-democratic current developed in the Soviet Union under Stalin.

The stab-in-the-back myth (German: Dolchstoßlegende, pronounced [ˈdɔlçʃtoːsleˌɡɛndə] , lit. 'dagger-stab legend') was an antisemitic and anti-communist conspiracy theory that was widely believed and promulgated in Germany after 1918. It maintained that the Imperial German Army did not lose World War I on the battlefield, but was instead betrayed by certain citizens on the home front – especially Jews, revolutionary socialists who fomented strikes and labour unrest, and republican politicians who had overthrown the House of Hohenzollern in the German Revolution of 1918–1919. Advocates of the myth denounced the German government leaders who had signed the Armistice of 11 November 1918 as the "November criminals" (November­verbrecher).

When Adolf Hitler and the Nazi Party rose to power in 1933, they made the conspiracy theory an integral part of their official history of the 1920s, portraying the Weimar Republic as the work of the "November criminals" who had "stabbed the nation in the back" in order to seize power. Nazi propaganda depicted Weimar Germany as "a morass of corruption, degeneracy, national humiliation, ruthless persecution of the honest 'national opposition' – fourteen years of rule by Jews, Marxists, and 'cultural Bolsheviks', who had at last been swept away by the National Socialist movement under Hitler and the victory of the 'national revolution' of 1933".

Karl Paul August Friedrich Liebknecht (/ˈliːpknɛxt/; German: [ˈliːpknɛçt] ; 13 August 1871 – 15 January 1919) was a German socialist politician and revolutionary. A leader of the far-left wing of the Social Democratic Party of Germany (SPD), Liebknecht was a co-founder of both the Spartacus League and Communist Party of Germany (KPD) along with Rosa Luxemburg.

Liebknecht was born in Leipzig as the son of SPD co-founder Wilhelm Liebknecht, and studied law and political economy. In 1907, he was imprisoned a year for writing an anti-militarism pamphlet, and in 1912 was elected to the Reichstag.

The Spartacus League (German: Spartakusbund) was a left revolutionary movement organized in Germany during World War I and immediately thereafter. It was founded in August 1914 as the International Group by Rosa Luxemburg, Karl Liebknecht, Clara Zetkin, and other members of the Social Democratic Party of Germany (SPD) who were dissatisfied with the party's official policies in support of the war. In 1916 it renamed itself the Spartacus Group and in 1917 joined the Independent Social Democratic Party of Germany (USPD), which had split off from the SPD as its left wing faction.

During the November Revolution of 1918 that broke out across Germany at the end of the war, the Spartacus Group re-established itself as a nationwide, non-party organization called the "Spartacus League" with the goal of instituting a council republic that would include all of Germany. It became part of the Communist Party of Germany (KPD) when it was formed on 30 December 1918 and at that point ceased to exist as a separate entity.

The interwar Communist Party of Poland (Polish: Komunistyczna Partia Polski, KPP) was a communist party active in Poland during the Second Polish Republic. It resulted from a merger in December 1918 of the Social Democracy of the Kingdom of Poland and Lithuania (SDKPiL) and the Polish Socialist Party – Left (PPS – Left) into the Communist Workers' Party of Poland (Komunistyczna Partia Robotnicza Polski, KPRP). The communists were a small force in Polish politics.

The Communist Party of Poland (until 1925 the Communist Workers' Party of Poland) was an organization of the radical Left. Following the ideas of Rosa Luxemburg, the party's aim was to create a Polish Socialist Republic, to be included in the planned Pan-European Commonwealth of Socialist States. The party did not support the formation of the Second Polish Republic in 1918 and supported the Bolsheviks (led by Vladimir Lenin) in the 1920 Polish–Soviet War.

Communism in Poland can trace its origins to the late 19th century: the Marxist First Proletariat party was founded in 1882. Rosa Luxemburg (1871–1919) of the Social Democracy of the Kingdom of Poland and Lithuania (Socjaldemokracja Królestwa Polskiego i Litwy, SDKPiL) party and the publicist Stanisław Brzozowski (1878–1911) were important early Polish Marxists.

During the interwar period in the Second Polish Republic, some socialists formed the Communist Party of Poland (Komunistyczna Partia Polski, KPP). Most of the KPP's leaders and activists perished in the Soviet Union during Joseph Stalin's Great Purge in the 1930s, and the party was abolished by the Communist International (Comintern) in 1938.

The Social Democracy of the Kingdom of Poland and Lithuania (Polish: Socjaldemokracja Królestwa Polskiego i Litwy, SDKPiL), originally the Social Democracy of the Kingdom of Poland (SDKP), was a Marxist political party founded in 1893 and later served as an autonomous section of the Russian Social Democratic Labour Party. It later merged into the Communist Workers Party of Poland. Its most famous member was Rosa Luxemburg.