Why was the Berlin Wall built in 1961?

Do you think the building of the Berlin Wall shows that Communist control of East Germany was weak or that it was strong?

In 1960 and 1961, an increasing number of inhabitants of East Berlin, the communist-controlled part of Berlin, fled to the western part in order to escape the oppressive life under the communist German regime. This was a serious leak of labor force, population and skilled people. So, in 1961, the authorities of the German Democratic Republic (communist state) decided to erect a wall along the borders of the former Soviet occupation zone with the Western-controlled parts of the city to stop this exodus.

The Berlin Wall became a symbol of the division of Germany and Europe into two opposed camps politically, militarily and ideologically.

Bulding a wall showed that the communist regime was not attractive to many Eastern German, that they preferred to live in a democratic and more prosperous western part of Germany. So, building the wall was a supposed show of force and authority, but it revealed the political weakness of the communist model.