quality:corruption
Start of the construction (1961)

On 15 June 1961, First Secretary of the Socialist Unity Party and GDR State Council chairman Walter Ulbricht stated in an international press conference, "Niemand hat die Absicht, eine Mauer zu errichten!" (No one has the intention of erecting a wall!). It was the first time the colloquial term Mauer (wall) had been used in this context.

The transcript of a telephone call between Nikita Khrushchev and Ulbricht, on 1 August in the same year, suggests that the initiative for the construction of the Wall came from Khrushchev. However, other sources suggest that Khrushchev had initially been wary about building a wall, fearing negative Western reaction. Nevertheless, Ulbricht had pushed for a border closure for some time, arguing that East Germany's existence was at stake.

Khrushchev had become emboldened upon seeing US president John F. Kennedy 's youth and inexperience, which he considered a weakness. In the 1961 Vienna summit, Kennedy made the error of admitting that the US would not actively oppose the building of a barrier. A feeling of miscalculation and failure immediately afterwards was admitted by Kennedy in a candid interview with New York Times columnist James "Scotty" Reston. On Saturday, 12 August 1961, the leaders of the GDR attended a garden party at a government guesthouse in Döllnsee, in a wooded area to the north of East Berlin. There, Ulbricht signed the order to close the border and erect a wall.

At midnight, the police and units of the East German army began to close the border and, by Sunday morning, 13 August, the border with West Berlin was closed. East German troops and workers had begun to tear up streets running alongside the border to make them impassable to most vehicles and to install barbed wire entanglements and fences along the 156 km (97 mi) around the three western sectors, and the 43 km (27 mi) that divided West and East Berlin. The date of 13 August became commonly referred to as Barbed Wire Sunday in Germany.

The barrier was built inside East Berlin on East German territory to ensure that it did not encroach on West Berlin at any point. Generally, the Wall was only slightly inside East Berlin, but in a few places it was some distance from the legal border, most notably at Potsdamer Bahnhof and the Lenné Triangle that is now much of the Potsdamer Platz development.

Later, the initial barrier was built up into the Wall proper, the first concrete elements and large blocks being put in place on 17 August. During the construction of the Wall, National People's Army (NVA) and Combat Groups of the Working Class (KdA) soldiers stood in front of it with orders to shoot anyone who attempted to defect. Additionally, chain fences, walls, minefields and other obstacles were installed along the length of East Germany's western border with West Germany proper. A wide no man's land was cleared as well to provide a better overview and a clear line of fire at fleeing refugees.