### Instruction:
What was the primary reason for constructing the Berlin Wall?

### Input:
The Berlin Wall (German: Berliner Mauer, pronounced [bɛʁˌliːnɐ ˈmaʊ̯ɐ] (listen)) was a guarded concrete barrier that encircled West Berlin of the Federal Republic of Germany (FRG) from 1961 to 1989, separating it from East Berlin and the German Democratic Republic (GDR) (GDR). Construction of the Berlin Wall was commenced by the government of the GDR on 13 August 1961. It included guard towers placed along large concrete walls, accompanied by a wide area (later known as the "death strip") that contained anti-vehicle trenches, beds of nails and other defenses. The primary intention for the Wall's construction was to prevent East German citizens from fleeing to the West.

### Response:
The Berlin Wall was primarily constructed to prevent East German citizens from fleeing to the West.