On Saturday 12 August 1961, the leaders of East Germany attended a garden party at a government guesthouse in Döllnsee, in a wooded area to the north of East Berlin, and Walter Ulbricht signed the order to close the border and erect a Wall.
On 30 August 1961, in response to moves by the Soviet Union to cut off access to Berlin, President Kennedy ordered 148,000 Guardsmen and Reservists to active duty.