In 1950's, thousands of people living in East germany went into West Berlin and never came back( most were skilled workers which caused problems for USSR)
By 1961, JFK came into power for USA and krushchev thought he could bully the young president
Khrushchev demanded that USA withdraw troops from Berlin, Kennedy refused
At two o clock in the morning on Sunday 13th August 1961, east German soldiers built a barbed-wire barrier along the entire frontier between east and west berlin
The barbed-wire fence was quickly replaced with concreate wall and all crossing points between east and west berlin were sealed, except one "checkpoint Charlie"
In October 1961, US diplomats and troops constantly crossed into East berlin, to find out how soviets would react
on the 27th October 1961, soviet tanks at checkpoint Charlie refused any further access into east berlin, for 18 hours US and soviet tanks were in a stand-off. Eventually the tanks slowly moved back, avoiding an outbreak of war
Berlin wall was dismantled on the 4th November 1989 and Germany became unified October 3rd 1990