The Communist Party of South Africa (CPSA) was unprecedentedly active during the 1940s. From its isolated and ineffectual position in 1940, Communists had established an unmatched presence in the black trade union movement and a considerable influence in South Africa's urban locations by 1945. The transformation of activity that followed the invasion of Russia expanded the Party's membership from a mere four hundred in 1941, to between 2-3,000 by the war's end. Communists abandoned all pretense at upholding the principle of a Leninist vanguard and committed themselves to achieving a mass membership. Yet for all its activity, and in spite of its increased size during the 1940s, the CPSA failed to establish a mass following among the African working class, and delegates to the Party's last annual conference in 1950 expressed considerable disappointment at the progress made.1 This article briefly outlines the growth of Communist activity among African workers and seeks to understand why the Party failed to win mass support.2