The Withdrawal from Dunkirk by Charles Cundall, June 1940 (© Charles Ernest Cundall/ IWM via Getty Images)

Operation Dynamo: Things You Need to Know about the Dunkirk Evacuation

Early in the Second World War, in late May 1940, the Allied forces of British, French and Belgian troops were trapped by the invading German army on the coast of France and Belgium, in the area around Dunkirk. The desperate and near-miraculous rescue that followed – controlled from Dover Castle – saved the Allied cause in Europe from total collapse, and was the biggest evacuation in military history. Find out the key facts about Operation Dynamo here.

Why were the Allies at Dunkirk?

Troops of the British Expeditionary Force marching through the ruined port of Dunkirk in May 1940

Troops of the British Expeditionary Force marching through the ruined port of Dunkirk in May 1940 © Popperfoto/Getty Images

The Second World War had begun in western Europe on 1 September 1939, when Germany invaded Poland. In Belgium and France there was a long winter of waiting as German and Allied forces, including the British Expeditionary Force (BEF), faced each other along the border defences.

Then on 10 May 1940, two German armies moved eastward. A smaller one swept through Holland and Belgium into northern France, drawing the main Allied forces north to meet it. The other, main German force advanced through Luxembourg, broke through the French lines at Sedan, and sliced across northern France to the coast. Moving rapidly with armoured columns, these armies trapped the Allies in an ever-decreasing pocket.

The Germans took Boulogne on 25 May and Calais the next day, leaving Dunkirk as the only viable port from which the BEF, part of the French army and the remains of the Belgian army could escape.

What was Operation Dynamo?

Vice Admiral Ramsay on the balcony of the Casemate tunnels at Dover Castle in April 1941

Vice Admiral Ramsay on the balcony of the Casemate tunnels at Dover Castle in April 1941 © Topical Press Agency/Getty Images

Operation Dynamo was the rescue operation implemented by the Royal Navy. It was co-ordinated by Vice Admiral Bertram Ramsay and his small team in Dover Castle. There, beneath the fortress, a network of tunnels deep within the cliffs became the nerve centre controlling the evacuation of Allied forces.

From 19 May, realising that rescue by sea would be necessary, Ramsay and his staff at Dover were making plans and arranging for ships to evacuate the BEF. On 26 May they were ordered to put their plans into action.

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Why Was it Called Operation Dynamo?

The reconstructed coastal artillery operations room within the Dover Castle tunnels

The reconstructed coastal artillery operations room within the Dover Castle tunnels

It’s sometimes stated that Operation Dynamo took its name from a room in the Dover Castle tunnels which had once held a dynamo – a machine that generated electricity. However, there’s no evidence for this. Dynamo was just a code word.

The tunnels below the castle, which were first dug during the Napoleonic wars, continued to play a vital role in the war effort after Dunkirk. From 1943 they served as a combined headquarters for all three services – army, navy and air force.

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Why Was Evacuation from Dunkirk so Difficult?

Troops on the beach at Dunkirk awaiting evacuation

Troops on the beach at Dunkirk awaiting evacuation © Topical Press Agency/Getty Images

The Allies had to defend a small pocket around Dunkirk that was under constant attack. Many thousands of men were crammed into streets and buildings, and along the beaches – so they were very vulnerable to intense German air attacks and shelling. There was little time to plan and organise an orderly evacuation, and effective means of communication were scarce.

The Germans had put the main docks at Dunkirk – the best place from which to evacuate troops – out of action. The two alternatives – the spindly breakwater, or mole, on the east side of the harbour, and the beaches to the north of the port –  were far from ideal. The beaches at Dunkirk shelve gently into the sea. Even at high tide, a destroyer couldn’t approach within a mile of the shore, and troops had to be ferried out in small craft.

Rescue was painfully slow at first – only 8,000 men were rescued on the first day. It took several days for the operation to gather pace.

What did the ‘little ships’ do during the Evacuation from Dunkirk?

Small craft on their way up the Thames in London on 4 June 1940, after taking part in the evacuation

Small craft on their way up the Thames in London on 4 June 1940, after taking part in the evacuation © Hulton-Deutsch Collection/CORBIS/Corbis via Getty Images

The little ships played an important part in the evacuation. Ramsay and his team quickly realised that small boats would be able to get close to the beach and ferry the troops out to larger ships. By 31 May, hundreds of civilian vessels – from fishing smacks and cockle boats to lifeboats and sailing barges – had answered the Royal Navy’s call for help and crossed the English Channel to Dunkirk.

Crewed mainly by volunteers, these tiny vessels bravely and repeatedly picked up soldiers queuing patiently on the beaches and in the water, and ferried them out to the waiting larger ships, under severe attack from German aircraft and artillery. Many also took troops back across the Channel themselves.

But it’s a common misconception that the little ships evacuated most of the men. In fact, over two-thirds (239,465) reached safety via the mole, while 98,761 were rescued from the beaches. And the role of the Royal Navy, especially its destroyers, was paramount in the operation. Its ‘big ships’ – mainly destroyers, minesweepers and requisitioned merchant vessels with naval crews – crossed to Dunkirk time and time again, without rest, and suffered terrible losses.

Operation Dynamo: Key Numbers

  • Dates: 26 May – 4 June 1940
  • Number of troops rescued: 338,226 including 224,320 British
  • Ships involved: 933
  • Ships lost: 236

Was the Dunkirk Evacuation a Disaster or a Triumph?

Destroyers filled with evacuated British troops arriving at Dover on 31 May 1940

Destroyers filled with evacuated British troops arriving at Dover on 31 May 1940 © Photo by Puttnam and Malindine/ IWM via Getty Images

Dunkirk, and the surrender of France that followed some three weeks later, left Britain isolated, vulnerable and under threat of imminent invasion. The BEF had abandoned or destroyed nearly all its heavy equipment at Dunkirk. Hitler declared the evacuation a decisive victory for Germany.

But by rescuing the bulk of the army, in what was the biggest evacuation in military history, Operation Dynamo returned to Britain a priceless asset – most of her trained and experienced troops. If they had been lost, the whole conflict might have taken a very different course. It was a critical moment for Britain in the Second World War.

‘We must be very careful not to assign to this deliverance the attributes of a victory. Wars are not won by evacuations.’ Winston Churchill, 4 June 1940

What was the ‘Dunkirk Miracle’?

Prime Minister Winston Churchill on the Casemate balcony at Dover Castle on 28 August 1940, watching the Battle of Britain

Prime Minister Winston Churchill on the Casemate balcony at Dover Castle on 28 August 1940, watching the Battle of Britain © Photo by Capt. Horton/ IWM via Getty Images

The evacuation was publicised as a miracle to boost public morale. The successful rescue, across seas that stayed unusually calm for nine days, was thereafter referred to as ‘the miracle of Dunkirk’.

But as well as this, the terrifying prospect that the depleted British armed forces might have to fight the Germans on home soil caused the nation, galvanised under Winston Churchill, to devote itself entirely to war. It did so not only effectively but, perhaps surprisingly, with total confidence in eventual victory. The ‘Dunkirk spirit’, reflecting a nation united and working against apparently impossible odds to thwart Hitler's ambitions, was born.

    

Top image: The Withdrawal from Dunkirk by Charles Ernest Cundall, June 1940 (© IWM via Getty Images)

Find out more

  • Touring the wartime tunnels at Dover Castle

    Operation Dynamo and the Dover Tunnels

    Find out how you can immerse yourself in the drama of the Dunkirk evacuation, in the very tunnels where Operation Dynamo was masterminded.

  • Wrens in front of the Officers’ Mess at Dover Castle

    Dunkirk on the Home Front

    Read some of the personal stories of what it was like to work in the tunnels beneath Dover Castle in the gruelling, hot days of May and June 1940.

  • Aerial view of Dover Castle, Dover, Kent

    History of Dover Castle

    Learn about the long history of the castle, from its likely origins as an Iron Age hillfort to its role in the Cold War.

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