Seventy years ago, as the Spanish Republic faced an internal military revolt led by General Francisco Franco, compounded by an external fascist invasion, the progressive and anti-fascist youth of the world adopted the Spanish rallying cry “¡No Pasarán!,” or “They Shall Not Pass,” as the mantra of their generation’s struggle against fascism and war. Spain was far more than a symbolic struggle for anti-fascist youth, but quickly became, especially for Communist youth, an ideological testing ground for putting Popular Front theory into practice. The Spanish anti-fascist struggle permeated the literature and campaigns of the Young Communist League USA, showing anti-fascist youth of their generation the Communists’ sincere dedication to the causes of internationalism, peace and democracy. The historical political lesson learned and applied by the YCL in Spain was that only through complete unity could youth battle the reactionary social forces that were bent on unleashing fascism and imperialist war upon the world.