The existence of West Berlin, a conspicuously capitalist city deep within communist East Germany, "stuck like a bone in the Soviet throat," as Soviet leader Nikita Khrushchev put it. The Russians began maneuvering to drive the United States, Britain and France out of the city for good. In 1948, a Soviet blockade of West Berlin aimed to starve the western Allies out of the city. Instead of retreating, however, the United States and its allies supplied their sectors of the city from the air. This effort, known as the Berlin Airlift, lasted for more than a year and delivered more than 2.3 million tons of food, fuel and other goods to West Berlin. The Soviets called off the blockade in 1949. After a decade of relative calm, tensions flared again in 1958. For the next three years, the Soviets emboldened by the successful launch of the Sputnik satellite the year before and embarrassed by the seemingly endless flow of refugees from east to west (nearly 3 million in the decade since the end of the blockade, many of them young skilled workers such as doctors, teachers and engineers) blustered and made threats, while the Allies resisted. Summits, conferences and other negotiations came and went without resolution. Meanwhile, the flood of refugees continued. In June 1961, some 19,000 people left the GDR through Berlin. The following month, 30,000 fled. In the first 11 days of August, 16,000 East Germans crossed the border into West Berlin, and on August 12 some 2,400 followed the largest number of defectors ever to leave East Germany in a single day.

All of the following measures failed to stop migration from East Germany EXCEPT

A. the Soviet blockade to starve the western Allies out of the city
B. technological advances such as the successful launch of the Sputnik
C. continued blustering and threats in the late 1950s and early 1960s
D. negotiations, summits, and conferences to put an end to the East-West conflict
E. supply of provisions through the air to East German cities
_________________