In 1958 Nikita Khrushchev demanded withdrawal of the US, French and British forces from Berlin. It was caused, among other things, by the worsening demographic situation in East Germany - after the Berlin partition over 3 million Germans fled to the west, not wanting to live in a communist country. The talks between the USSR and the US did not lead to an agreement, so in 1961 Khrushchev reissued an ultimatum on the subject of the western forces withdrawal which was rejected by the US. On 13 August 1961, the GDR responded by building the Berlin Wall, one of the most meaningful symbols of the Cold War. In the following years many poople died, trying to get to the other side of the wall (often shot by guards).
The Berlin Wall divided Berlin for 28 years.