By Nick Thorpe
BBC News, Budapest
Thousands of people flooded out of the Soviet bloc via Hungary
Exactly 20 years ago Hungarian border guards began dismantling the physical barrier along the Hungarian-Austrian border known as the Iron Curtain.
It was an act with huge consequences for other Eastern European countries and eventually the whole of Europe.
Only a tiny section of the Iron Curtain was removed on 2 May 1989 - about 8 km in total, either side of four border crossings between Hungary and Austria.
But it was an act of massive moral and political importance.
Hungary defied its supposed allies in the Eastern Bloc, especially East Germany, Czechoslovakia and Romania, while the then Soviet leader Mikhail Gorbachev looked on impassively.
The main reformer in the Communist Party in Hungary at that time, Imre Pozsgay, claims the main credit for bringing down the curtain.
"I didn't do anything heroic, but I knew how much we could get away with," he said.
As word spread of the breach in the Iron Curtain, thousands of East Germans and Romanians headed for it, and the border guards were overwhelmed.
By September 1989 Hungary gave up all pretence of acting as the loyal guard of the socialist camp and opened its western border completely.
Within three months, the communist system collapsed throughout the region.