This wall – in fact a complex system of defensive elements (wall, barbed wire, watchtowers, etc.) – was erected on the night of the 12th and 13th of August 1961 under the orders of the authorities of the German Democratic Republic (GDR). It thus completely isolated West Berlin (the French, English and American sectors of the old German capital) from the rest of the GDR. The decision to build it was taken to try to stem the haemorrhage of the population registered in the GDR: it is in effect estimated that between 1949 and 1961 around 3 million inhabitants left the GDR for the Federal Republic of Germany (FRG), mainly through East Berlin. Following the decision of the East German authorities to allow its nationals to travel without any restrictions, the crowds hurried to the foot of the Wall on the night of 9th and 10th November 1989. Overwhelmed, the border guards, who had received no instructions, let the crowd pass: it was the fall of the Berlin Wall, the prelude to German reunification.