How the Berlin Wall fell. In order to calm mounting protests GDR officials decided on loosening travel restrictions between East and West, not open the border completely.
Notes of the new rules had been handed to a spokesman who hadn't had time to read them before the press conference.
"Private travel outside the country can now be applied for without prerequisites," he said. Surprised journalists clamoured for more details.
Shuffling through his notes, he said that as far as he was aware, it was effective immediately.
In fact it had been planned to start the next day, with details on applying for a visa.
But the news was all over television – and East Germans flocked to the border in huge numbers.
As the border became inundated with East Berliners wishing to reunite with family and/or escape the GDR, border guards became overwhelmed and with no orders to either shoot upon the crowd or open the gate, only a handful of guards facing hundreds and thousands of citizens, rather than fire and create a stampede and potentially kill hundreds the head of the guards decided to give the order "Open the barrier!"
What came next was a spontaneous chain reaction with Berliners on both sides arriving at Checkpoint Charlie to celebrate this momentous event and to demolish the wall.
So basically an ill prepared functionary made a flippant remark and a border guard captain unable to get orders on how to proceed led to one of the most defining moments of the late 20th Century in Europe.