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.
Menurut The God that Failed oleh Arthur Koestler, mantan anggota Partai Komunis Jerman, partai komunis terbesar di Eropa Barat pada masa antara Perang Dunia I dan Perang Dunia II, kaum komunis, bersekutu dengan Uni Soviet, terus mempertimbangkan "fasis sosial" Partai Sosial Demokrat Jerman menjadi musuh yang sebenarnya di Jerman, bahkan setelah Partai Nazi meraih kekuasaan.