Operation Dynamo was the name given to the mass evacuation during the Battle of Dunkirk conducted from 27 May to 4 June 1940. In nine days, 338,226 French and British soldiers were taken off the beach by a ragtag fleet of over nine hundred vessels. These vessels, now known as the "Little Ships of Dunkirk" were mainly a mixture of merchant marine vessels, fishing boats, pleasure craft and RNLI lifeboats, whose details had been requisitioned by the Admiralty on May 14. If the owners could not be contacted, some available ships were simply commandeered for use in the operation. Though the "Miracle of the Little Ships" is a major folk memory (at the time a useful propaganda tool too), and indeed small excursion steamers, pleasure boats and even rowboats did help evacuate troops from the beaches; over 80% of the troops evacuated were actually taken off the harbour's protective mole by destroyers and larger ships.

Despite the success of this operation, over fifty thousand vehicles and forty thousand French troops were abandoned after a valiant rearguard action. The British also lost 235 ships of various types.