What led to the construction of the Berlin Wall?

During the Cold War, Berlin was split amongst the Allies and the Soviets. The West was democratic, and the East was Communist. To prevent Eastern refugees from fleeing to the West, the Communists built a wall that completely sealed off the West from the East. This was the Berlin Wall.

There was a refugee crisis in Berlin, where East Berliners would flee to West Berlin in the prospect of employment, more freedom and a better standard of living. East Berlin was ruled by the communist Soviet Union, and West Berlin by the capitalist USA. The emigration of East Berliners to West Berlin created a propaganda crisis for the Soviet Union as it showed the world that people preferred capitalism over communism. The wall was built to stop people fleeing.