Operation Dynamo began on 26 May 1940 because the British Expeditionary Force and other Allied troops were running out of ground to hold.

The German advance through France and Belgium had pushed Allied forces back towards the Channel. Dunkirk became one of the few remaining exits. The operation would later be remembered as a rescue, with small ships, crowded beaches and exhausted men coming home. At the start, it was harsher than that. Britain was trying to save an army from a failed campaign.

The Royal Navy had the central job. The evacuation had to be organised across the harbour, the mole and the beaches, with men waiting under air attack and no certainty that enough ships could reach them in time. Dunkirk’s harbour was damaged, the beaches were exposed, and the numbers waiting were far beyond what anyone would want to manage under fire.

The beaches became the lasting image, but they were only part of the work. The East Mole, a long breakwater, became one of the most important routes out of the harbour. Men could board ships more quickly there than from open sand. Time was short. Every hour brought more risk from air attack, confusion, exhaustion and the German forces closing in around the perimeter.

Civilian vessels later became central to the public memory of Dunkirk. Fishing boats, pleasure craft, lifeboats and other small vessels crossed the Channel or helped carry men from the beaches to larger ships offshore. They deserve their place in the story. Even so, the evacuation was not simply a spontaneous national rescue. It depended on naval command, military discipline, larger ships, harbour work and the Allied troops holding the defensive perimeter.

By the time Operation Dynamo ended on 4 June, more than 338,000 British and Allied troops had been brought out. That changed Britain’s position. The country had lost the campaign in France, but it had not lost its core army. The men rescued from Dunkirk could be re-formed, re-equipped and used again.

The cost remained severe. Many men were killed, captured or left behind. Heavy equipment, vehicles and weapons were abandoned. France was still falling. Dunkirk did not undo the defeat that necessitated the evacuation.

That was the balance Churchill had to hold. Relief was real. So was danger. Britain had avoided a deeper military disaster, and the rescue gave the countrymen time and morale. Yet it was still an evacuation from a collapsing front.

Operation Dynamo matters because it kept Britain in the war at a point when losing the army might have changed everything. It was a rescue from defeat rather than a victory.