On 10 May 1940, German troops entered Belgium and the Netherlands, and marched towards the English Channel. All attempts to thwart German progress failed, apart from a few short-lasting victories, such as the Battle of Arras on 21 May, which halted the Wehrmacht in their tracks for 24 hours. As disaster loomed, Churchill himself ordered the start of the Operation on the evening of 26 May.
The Operation was named after the Dynamo room located below Dover castle, the headquarters of the British Royal Navy, which supplied the building with electricity. This was where British Vice-Admiral Bertram Ramsay planned the Operation as from 20 May.
The Operation was launched on 27 May 1940. Around 850 British, Belgian, Dutch and French warships started the evacuation, but it was not enough. Around 700 private ships joined in the Operation, including merchant marine boats, fishing boats and pleasure craft, often but not always with the owner's permission. Many boat owners actually asked to take part. These vessels were later nicknamed the "little ships of Dunkirk". Nearly 400,000 troops were stranded in Dunkirk and on the beaches, as well as in some outlying villages.
Meanwhile, many British and French soldiers continued to fight to prevent the German army from taking the city and ensure evacuation could take place.
Evacuation conditions were difficult given the bombing and frequent attacks by the Luftwaffe (German Air Force) on the beaches and boats. The Royal Air Force also contributed greatly to the success of the Operation, although they rarely get any credit for it.
Many considered the Operation to be a great success. From the port and beaches of Dunkirk: 338,226 soldiers were evacuated (198,229 British troops and 139,997 French). However, between 35 and 40,000 soldiers were left behind, mainly French. Practically all the heavy artillery and vehicles were abandoned. In all, 2,472 cannons, around 65,000 vehicles and 20,000 motorcycles were left behind in France, as well as 377,000 tonnes of supplies, over 68,000 tonnes of munitions and 147,000 tonnes of fuel.
The Operation had many major consequences. It meant the Allied Forces could keep a large number of seasoned troops, forming the basis of the troops who were to recapture France. Even though most of the French soldiers were demobilised and sent back to France after the Armistice. Churchill dubbed Operation Dynamo "The miracle of Dunkirk", yet reminded everyone that "Wars are not won by evacuations".