Gort had warned the British government that the BEF would have to be evacuated, and as a result the evacuation from France was a well-planned and controlled operation. More than half the men were taken off from Dunkirk harbour. The rest slept exhausted on the sand dunes nearby and then, following detailed orders, filed down to the edge of the wide beaches. From there small boats, towed over and manned by their civilian owners, ferried them out to larger craft like destroyers, merchantmen, liners, paddlesteamers, fishing boats, barges and private yachts. The Royal Navy had assembled them from all round southern England. (There were 765 in all, of which 2 were lost when the weather was calm. Luftwaffe (German air force) bombed the beaches and the ships, which meant that the evacuation had to take place at night but the RAF (the British Royal Air Force), prevented their bombing altogether. The German army was held off for nine days and all the BEF (a total of 340000 men where120000 were French) were rescued. Their tanks, guns and transport had to be left behind. The French held the shrinking area around Dunkirk for the last two days and 40000 of them were left behind. The evacuation was a remarkable achievement. The total loss of the BEF would have been a crushing disaster for Britain.

The Germans turned swiftly to overwhelm France with 140 divisions against 65 French divisions. Guderian's tanks exploited a breakthrough on the left and surged forwards, surrounding a whole French army. The German general, Kleist, made a panzer drive in the centre. The Maginot Line was pierced in two places. The French, army, no longer an efficient fighting force, made a disorderly retreat and the Germans overran much of France. The French government fled from Paris in confusion and on 22 June the French Marshal Pétain signed a humiliating armistice with the Germans. The Germans occupied northern France and the south was to be ruled independently by a puppet government, based at Vichy and led by Pétain. Meanwhile Italy had declared war on France and Britain, and had attacked France in the south.

Many people thought Britain would now have to make peace with Germany but when Hitler offered lenient peace terms Churchill ignored them. Hitler had not planned to attack Britain, his main aim being the conquest of the Soviet Union and his actions against France and Britain were to prevent them from interfering with this. But when Britain refused to make peace Hitler reluctantly ordered the preparation of a plan for her invasion. This hastily drawn-up plan was called 'Operation Sealion'.