After Joseph Stalin consolidated power in the Soviet Union, the Comintern launched a campaign against the reformist movement by denouncing them as "social fascists". According to The God that Failed by Arthur Koestler, a former member of the Communist Party of Germany, the largest communist party in Western Europe in the Interwar period, communists, aligned with the Soviet Union, continued to consider the "social fascist" Social Democratic Party of Germany to be the real enemy in Germany even after the Nazi Party had gotten into power.[8]