Leftist Jewish immigrants who arrived in Argentina between the end of the 19th century and the Second World War came mainly from Eastern Europe. These were working families who spoke Yiddish and manifested a secular Judaism. Several had political experience in Marxist movements and brought their militant spirit to this new land. After the 1917 Russian Revolution, three political networks took shape in Argentina within the culture of the Jewish Left: the Socialists of the Workers’ Party Bund; the Marxist-Zionists of the Linke Poale Sion Party; and the Leninist communists linked to the Comintern and the Argentine Communist Party. The three groups were active founders of schools, theaters, publications, libraries, cultural centers and sports entities. However, the most radicalized sector, which confronted Hebrew Zionist nationalism, the religious sectors, and the warmongering in the Middle East, was the one concentrated under the Federación Yiddisher Kultur Farband (YKUF). Since 1935, when the 7th Congress of the Communist International called for the creation of Popular Fronts, this sector identified itself as “Judeo-progressive” (di progressive) and, in line with the Communist Party of the Soviet Union, fought against religion and Zionism throughout the twentieth century. This chapter contends that this identity, condensed under the Jewish antifascist and communist premises of the YKUF, was unconditionally faithful to the Soviet socialist system because it was born out of the influence of the October Revolution and the workers’ struggle, solidified during the Second World War due to the role of the Red Army against Nazism, and became unbreakable during the years of the Cold War against the struggle against imperialism in Latin America.