1) At 1.05am on Sunday 13 August 1961, East German border guards and army combat groups took up positions on the demarcation line at the Brandenburg Gate in central Berlin. In a scene repeated along the border dividing the two halves of the city, they ripped up the paving stones and strained barbed wire between concrete posts. By early morning, only 12 of the 81 street crossing points were passable (that was soon cut to seven). This was phase one of the Berlin Wall. 2) There is evidence that the building of the wall actually came as something of a relief to the western powers; they had been expecting such a move and saw it, if anything, as evidence that no imminent attempt was likely by the Soviet Union and GDR to retake all Berlin; west Berlin, in other words, was safe. 5) The fall, when it came, was quick. There were large demonstrations in the GDR in September 1989. In October, the country’s lifelong leader, Erich Honecker, resigned. On 9 November, the East German authorities lifted border controls to the west, including for private journeys to west Berlin, from 17 November. Germany was formally reunified just 11 months later.
Which sentence gives the main idea of Paragraph (5)?