It is not possible to write on Slovak Communism, dividing it from Czechoslovakian communism. When in 1918 united state of Czechs and Slovaks was created, it brought with also unification of most political parties, including the communists. Development of communist ideas was supported by the influence of Bolshevik revolution in Russia, from where many Czechs and Slovaks, who were prisoned during the I World to Russia, got their first infection of communism. Majority of them nevertheless returned from Russia not with infection but with strong anti-communist understandings.
Formally founded in 1921, the Czechoslovakian Communist Party was one of some twenty political parties that competed within the democratic framework of pre-WWII Czechoslovakia, but it was never in government. Uniting both Slovak and Czech part of the country, it even worked with German and Hungarian minorities. As at the beginning Czechoslovakian communists tried to keep independent line, then with years they were pressed under string control of Comintern, turning more from parlamentarian fight to underground acitivtity. It decreased significantly its influence in Czechoslovakia, turning communists to some kind small secret sect, which at the same was strongly organized. During World War II many KSC leaders sought refuge in the Soviet Union, where they made preparations to increase the party's power base once the war ended.
In 1939 after the Nazis occupied Czechoslovakia, „puppet" state of Slovakia was created, which actually was fully controlled by the Germans. In March 1939 the Communist Party of Slovakia (Slovak: Komunistická strana Slovenska - KSS) was created, as the Slovakian branches of the Communist Party of Czechoslovakia (KSČ) were separated from the mother party. During the II World War communist partisan movement was developed on the territory of Slovakia. In 1944 the national resistance made the attempt to rise against the Nazis, but the uprising was crushed. As in other places in Central Eastern Europe the Red Army and communist partisans did not support the uprising, leaving it to their own fate. As Nazis annihilated national underground, who organized the uprisings, the power vacuum was created, which was effectively used by communists, returning to Slovakia together with the Red Army.
When Czechoslovakia was again established as a unified state, the KSS was still a separate party for a while (1945-1948). On September 29, 1948, it was reunited with the KSČ and continued to exist as an "organizational territorial unit of the KSČ on the territory of Slovakia". .After the merger KSS functioned as a regional affiliate of the KSČ, not as an independent political institution. Therefore, the organizational structure of the KSS mirrored that of the KSČ: the KSS Congress held session for several days every five years (and just before the KSČ's Congress), selecting its Central Committee members and candidate members, who in turn selected a Presidium, a Secretariat, and a First Secretary (i.e. party leader).