The East German regime, however, fought back. With still unhindered flight to the west a possibility, infiltration started on a grand scale and a reversal of sorts took hold. During the early 1960s as many as 90% of the BND's lower-level informants in East Germany worked as double agents for the East German security service, later known as Stasi. Several informants in East Berlin reported in June and July 1961 of street closures, clearing of fields, accumulation of building materials and police and army deployments in specific parts of the eastern sector, as well as other measures that BND determined could lead to a division of the city. However, the agency was reluctant to report communist initiatives and had no knowledge of the scope and timing because of conflicting inputs. The erection of the Berlin Wall on 13 August 1961 thus came as a surprise, and the BND's performance in the political field was thereafter often wrong and remained spotty and unimpressive. There was a great success for the Federal Intelligence Service during the Cuban Missile Crisis. In 1962, the BND was the first Western intelligence service to have information about the stationing of Soviet medium-range missiles on the caribbean island and passed it on to the United States. Between 1959 and 1961, Reinhard Gehlen called on Washington several times in vain to "insert the dangerous communist bastion, which at the same time represents an excellent starting point for the communist infiltration of Latin America, into the [USA] sphere of power by rapid access." Gehlen's influence on the US government should not be underestimated, because the BND was able to regularly provide the CIA with detailed information about Soviet arms deliveries through its very good sources in Cuba. There are indications that the secret service was also informed about military actions against Cuba. Ten days before the Bay of Pigs invasion, Gehlen reported to Bonn: "Within a relatively short period of time, large-scale military operations to defeat Fidel Castro will begin." In 1962, the BND also found out from its sources, the Cuban exiles living in Miami, that Cuba was also trying to get hold of weapons through German dealers. According to a BND report, Cuba was also able to recruit four former Waffen-SS officers as instructors for the Cuban armed forces. However, the identity of the men was blacked out in the report. "This negative view of BND was