In June 1940, some 340,000 retreating Allied troops with advancing German forces at their backs were forced to the beaches of France with nowhere to go. That's until hundreds of small boats from Britain showed to get them out.
The evacuation had been a turning point in the war that had allowed British troops to eventually return in the 1944 D-Day invasion that led to Germany's defeat.
Sixty-eight thousand troops at Dunkirk didn't make it but Prince Charles told the veterans in Dunkirk on Sunday that those lives were not lost in vain.
"Without the success of Operation Dynamo...without the sacrifice of those who never returned home, D-Day may never have taken place at all," he said.
It's the last time the evacuation will be marked...but it will always be remembered, in the words of Winston Churchill, as "the miracle of deliverance."
Snatching Britain from the jaws of defeat, Operation Dynamo gave birth to the never-say-die "Dunkirk spirit" that passed into British legend.
But for the veterans, sadness lurked behind the pageantry. They fell silent and let their banners drop to the ground as they remembered their epic flight.
"That is what gets you, if you go around the cemeteries and look at the ages of the blokes, 19 to 20, the poor sods got no life whatsoever," said 79-year-old Reginald Rymer.
Troops waited for days without food or water on the beaches, digging into the dunes with their bare hands to seek refuge from German dive-bombers or wading up to their necks in water to await rescue.
"It always brings tears to my eyes, even talking about it now," said Jim Sharples, 81.
Later the ships were due to sail out to sea and drop wreathes while a World War II Lancaster bomber would shower them with poppy petals.