Germany's partition in 1949 and its unification in 1990 provided the international community with one of the most interesting case studies of state succession and accession in the twentieth century. Important precedents were established for the legal status of divided states and their constituent parts, as well as for related issues of nationality and bilateral relations. / Quadripartite Agreement: Few could possibly have foreseen the sudden achievement of German unification in 1990. More than two decades earlier, in 1969, the social-liberal coalition government under Chancellor Willy Brandt had launched a new Eastern policy that seemed to perpetuate the status quo. Working in parallel with the détente between the Soviet Union and the United States, Bonn's Ostpolitik sought to normalize and improve relations in the heart of Europe. One of the most important outcomes of this policy was the Quadripartite Agreement, a complex web of multilateral and bilateral undertakings, notes, treaties, and statements negotiated between representatives of the Four Powers and the governments of the two German states, West Berlin, and several states in Eastern Europe. During the first phase of Ostpolitik, the Federal Republic laid the political foundations for the negotiations to follow by signing a series of bilateral treaties with states in Eastern Europe. First, to encourage Soviet cooperation, Bonn signed the nuclear Non-Proliferation Treaty and a major gas pipeline agreement.