Hungarian Foreign Minister Gyula Horn announced that Hungary would allow thousands of East German citizens camped along its border to cross freely into Austria, defying its Warsaw Pact obligations to prevent Western emigration. Within three days, over 13,000 East Germans streamed across, exposing the Iron Curtain's first real crack and accelerating the chain of events that would bring down the Berlin Wall two months later.
For weeks, thousands of East German 'vacationers' had been massing in makeshift camps in Hungary, having used the loophole of travel to a fellow socialist country to inch toward the West. Hungary's reformist government, itself edging away from Soviet orthodoxy, faced a choice: honor a bilateral treaty with East Germany requiring it to turn these people back, or let them go.
Foreign Minister Gyula Horn announced on state television that the border would open at midnight. It was a quiet sentence with seismic consequences — the first time since the Iron Curtain's construction that a Warsaw Pact state had deliberately let its citizens flee westward en masse.
More than 13,000 East Germans crossed within three days, family station wagons abandoned by the roadside, refugees walking the last stretch on foot into Austria. East Berlin was furious, but Hungary held firm. The move emboldened protest movements across the Eastern bloc and is widely credited by historians as the first domino in the sequence that ended with the fall of the Berlin Wall that November and, within two years, the collapse of the Soviet Union itself.