Officially, East Germany and Poland were “socialist brother countries.” But new evidence reveals that their intelligence services shared a mutual distrust and dislike. Many Polish journalists describe the relationship between the People’s Republic of Poland and the German Democratic Republic until the fall of the Berlin Wall as a “forced friendship.” Even if the rulers of both countries celebrated their harmonious alliance in public, behind the scenes there was a profound distrust between Warsaw and East Berlin. Many Poles considered their neighbors on the Western side of the Oder River as potentially dangerous “red Prussians,” while East Germans considered their Polish comrades as unreliable allies whose liberal reforms put the whole Communist bloc at risk. For a long time, it was believed that the relationship between the countries’ secret services was an exception to this rule: The fact that both agencies shared a common enemy in the West meant they were supposed to cooperate closely. According to new archive evidence, this was not the case: While the rivalry between the two countries was palpable on a political and social level.