The Post-War Era and Unification: In the aftermath of World War II (1939–45) and following occupation by the victorious powers (the United States, the Soviet Union, Britain, and France), Germany came to consist of two states. One, East Germany, never attained real legitimacy in the eyes of its citizens, fell farther and farther behind economically, and had to use force to prevent its population from fleeing to the West. The other, West Germany, was resoundingly successful. Within two decades of defeat, it had become one of the world's richest nations, with a prosperity that extended to all segments of the population. The economy performed so successfully that eventually several million foreigners came to West Germany to work as well. West German and foreign workers alike were protected from need arising from sickness, accidents, and old age by an extensive, mostly nongovernment welfare system. In 1990 German unification overcame the geographic separation of the two German states, including an infamous wall between West Berlin and East Berlin, but economic integration still has not been achieved satisfactorily. In the first decade of the twenty-first century, the forces of globalization are posing a renewed challenge to the social-market economy in place throughout the nation.