The German army had taken just ten days to reach the English Channel and could very easily have cut off the Allied armies. Unable to believe the ease with which he had overcome a numerically superior enemy, however, Hitler ordered his generals to halt their lightning advance, giving Allied forces trapped in the Pas-de-Calais enough time to organize Operation Dynamo, the largest wartime evacuation ever undertaken. Initially it was hoped that around 10,000 men would be saved, but thanks to low-lying cloud and the assistance of over 1750 vessels - among them pleasure cruisers, fishing boats and river ferries - 140,000 French and over 200,000 British soldiers were successfully shipped back to England.

In France, the ratio of British to French evacuees caused bitter resentment, since Churchill had promised that the two sides would go bras dessus, bras dessous ("arm in arm"). Meanwhile, the British media played up the "remarkable discipline" of the troops as they waited to embark, the "victory" of the RAF over the Luftwaffe and the "disintegration" of the French army all around. In fact, there was widespread indiscipline in the early stages as men fought for places on board; the battle for the skies was evenly matched; and the French fought long and hard to cover the whole operation, some 150,000 of them remaining behind to become prisoners of war. In addition, the Allies lost seven destroyers and 177 fighter planes and were forced to abandon over 60,000 vehicles.