A former eastern European country. It emerged in 1949 from the Soviet Zone of occupation of Germany. Its frontier with Poland on the Oder-Neisse line, agreed at the Potsdam Conference, was confirmed by the Treaty of Zgorzelec in 1950. Its capital was East Berlin, but the status of West Berlin,—an enclave of the Federal Republic of Germany 150 km (93 miles) inside East German territory, whose existence was guaranteed by the Four-Power Agreement between the victorious allied powers—caused serious problems (see berlin airlift). In the first five years the republic had to pay heavy reparations to the Soviet Union, and Soviet troops were used to put down disorder in 1953. In 1954, however, the republic proclaimed itself a sovereign state and in the following year became a founder-member of the Warsaw Pact. In 1956 the National People’s Army was formed; this organization was instrumental in sealing the GDR’s borders in August 1961 (including erecting the Berlin Wall) to prevent large-scale emigration to West Germany. Walter Ulbricht (1893–1973) was General Secretary of the ruling Socialist Unity Party (1946–71) and Chairman of the Council of State (1960–71). In 1972 the German Federal Republic, as part of the policy of Ostpolitik, established diplomatic relations with the republic. Admission to the UN followed in 1973, after which the republic was universally recognized. Although economic recovery from World War II was slower than in the west, East Germany, under Erich Honecker (Chairman of the Council of State, 1976–89), succeeded in establishing a stronger industrial base than most of its fellow members of COMECON. However, its highly bureaucratic, centralized system of control steadily atrophied, corruption spread from the top, and its secret police, the Stasi, became ever more ruthless. During 1989 a series of huge demonstrations took place, mostly in Berlin and Leipzig, with a new political grouping, New Forum, demanding democratic reforms. In November 1989 the Berlin Wall was opened and the communist monopoly of power collapsed. The first free elections since 1933 were held in March 1990, with the conservative Christian Democratic Union emerging victorious, and on 3 October 1990 the republic ceased to exist, being absorbed into the Federal Republic of Germany. Criminal proceedings were instituted against those who were deemed to have committed human rights abuses in the GDR regime, but few were punished. The case against Erich Honecker was dropped due to his ill-health. His successor, Egon Krenz, and several officials were found guilty of various crimes, notably ordering the shooting of refugees across the Berlin Wall.