In the tumultuous atmosphere of pre-Civil War Spain, leftist political factions sought to consolidate their forces to confront the growing threat of fascism, both at national and regional levels. On July 23, 1936, the Unified Socialist Party of Catalonia emerged as a result of the merger of the Socialist Party of Catalonia and the Communist Party of Catalonia. This union was significant not only for the political landscape of Catalonia but also for the larger context of Spain at that time, which teetered on the brink of civil war.

The decision to form this unified party was driven by the need for a cohesive and organized leftist front to resist the Nationalist forces led by Francisco Franco, who had been gaining momentum in various regions of Spain. Through this merger, the parties aimed to present a united front, advocating for socialist principles while also incorporating communist ideologies, which they believed were essential for effectively challenging the rising fascist sentiment.

The Unified Socialist Party of Catalonia worked to rally support from various labor organizations and leftist activists, fostering a spirit of solidarity among workers and intellectuals alike. This collaboration was crucial during the early stages of the Spanish Civil War, where both military and political strategies would evolve as leftist factions grappled with internal divisions and external pressures. The formation of this party underscored Catalonia's unique cultural and political identity within Spain and highlighted its role as a center of radical leftist politics during a time of crisis.