The Communist Party of Spain (Partido Comunista de España, PCE) was founded in 1921 in a context marked by social unrest and political turmoil in Spain. The formation followed the increasing influence of leftist ideologies across Europe after World War I and the Russian Revolution. The founders aimed to unite various socialist factions to create a cohesive front against the bourgeois state. They sought to address the dire economic conditions faced by the working class through a revolutionary framework. Alongside its establishment, the party published the inaugural edition of 'Mundo Obrero' (Workers' World), which served as an official mouthpiece for the party's ideas and policies. The newspaper aimed to inform, educate, and mobilize workers around socialist ideas, advocating for labor rights and social justice.

In the initial years, the PCE faced numerous challenges, including repression by the Spanish government, which viewed the party as a threat to its authority. However, the party gradually gained traction within labor movements and among intellectuals, which helped establish its presence in Spanish politics. The publication of 'Mundo Obrero' became a key tool for the party's outreach efforts, disseminating critical information on labor rights and articulating the political agenda of the left. This period laid the groundwork for the later involvement of the PCE during the Spanish Civil War, where it played a pivotal role in the resistance against Franco's forces.

The creation of the Communist Party and 'Mundo Obrero' signified a crucial moment in Spain's political evolution, representing a shift toward organized leftist politics. This leftist surge was not only an effect of the domestic landscape but also reflected broader global trends towards communism and socialism in the early 20th century.