Ostpolitik during the era of Willy Brandt signaled a new departure in West German foreign policy. At first a latecomer in European détente, the Federal Republic of Germany (FRG) became its pacemaker. With respect to both security matters and economic relations, the FRG emerged as the main partner of the Soviet Union in Europe. Starting from the international context, the article analyzes the dynamic that emanated from the formula Wandel durch Annäherung (change through rapprochement). The focus is on (1) perceptions and short-term objectives, (2) underlying assumptions and expectations, and (3) the achievements of Ostpolitik. East-West relations were shaped by newly introduced methods of communication that opened avenues for détente and peaceful change. The experience of communicative actions led to a constellation of antagonistic cooperation in Europe. The East-West conflict continued, but conflict behavior had changed for good.