Dunkirk evacuation

By 21 May 1940, ten days after the German invasion of the Low Countries and France began, panzer divisions of Army Group A had reached the English Channel at Abbeville, sealing off the British Expeditionary Force, the Belgian army and the French First, Seventh and Ninth Armies in a shrinking pocket across northern France and Belgium. General Lord Gort, commanding the BEF, had already concluded by 19 May that evacuation by sea was the only realistic option, and planning for what became Operation Dynamo began under Vice Admiral Bertram Ramsay at Dover on 20 May, before the British government had formally sanctioned it and without informing the French.

The German halt order, issued by Generaloberst Gerd von Rundstedt on 23 May and approved by Hitler the next day, stopped the panzer divisions roughly fifteen miles from Dunkirk for some three days. Responsibility for destroying the trapped Allied armies passed to Göring's Luftwaffe. Historians still dispute the motives behind the halt — concern about tank losses, terrain unsuited to armour, and the wish to husband forces for the coming drive on Paris have all been cited — but the pause gave the Allies time to organise a defensive perimeter along the canals around Dunkirk and to begin the withdrawal in earnest. The order was rescinded on 26 May, the same day Dynamo formally began.

Evacuation proceeded far more slowly than hoped in its first days: only 7,669 men were lifted on 27 May. Dunkirk's harbour was wrecked by bombing, so William Tennant, sent to organise the embarkation, improvised loading directly onto destroyers from the East Mole, a breakwater never designed for the purpose, while other troops waded out from the beaches to be ferried to larger ships by the "Little Ships," several hundred requisitioned fishing boats, pleasure craft and lifeboats. The Belgian army surrendered on 28 May, exposing the eastern flank, and the perimeter was held by British and French divisions falling back through Poperinge, Furnes and the canal lines while, to the south, the French First Army under Molinié fought a costly delaying action around Lille from 28 to 31 May against seven German divisions, buying further time at Dunkirk before its 40,000 survivors were forced to surrender.

Numbers evacuated rose sharply once the mole was in use and the perimeter stabilised: 17,804 on 28 May, 47,310 on 29 May, 53,823 on 30 May, and a peak of 68,014 on 31 May. The Luftwaffe's "maximum effort" of 29 May and clear skies on 1 June, which cost four destroyers and dozens of smaller vessels, failed to stop the flow, partly because RAF Fighter Command, operating from bases in England far closer than the Luftwaffe's, contested the skies over the beaches despite being largely invisible to troops on the ground, who often felt abandoned by their own air force. The BEF's evacuation was essentially complete by 2 June; thereafter French troops, who had joined the lifts from 29 May, made up the bulk of those rescued, aided by Admiral Abrial's naval forces still holding the town. The last ships left in the early hours of 4 June, by which point roughly 40,000 French and British soldiers, mostly forming the rearguard, had been left behind to be taken prisoner.

In total 338,226 Allied soldiers were carried to England by a fleet of nearly 1,000 vessels, of which about 240 were lost. The BEF nonetheless lost some 68,000 men killed, wounded or captured during the French campaign and abandoned nearly all its tanks, guns and transport on the continent. Churchill, addressing the Commons on 4 June, called the episode "a colossal military disaster" while cautioning against mistaking the deliverance for a victory, since "wars are not won by evacuations."