Berlin Wall, the war of spies 

On the night of August 12 to 13, 1961, the Berlin Wall (called the "Wall of Shame" by West Germans) was built by the German Democratic Republic (GDR). Moving from a barbed iron curtain to a concrete wall, this historic construction will serve to put an end to the growing exodus of its inhabitants to the Federal Republic of Germany (FRG).
What was really hidden behind the creation of this wall? Was he only there to cover up an unarmed war?