The operation was launched after German "Blitzkrieg" tactics trapped the British Expeditionary Force (BEF) and elements of the French and Belgian armies against the English Channel.
While nearly 40 Royal Navy destroyers carried the bulk of the troops, over 800 small civilian vessels —including fishing boats, yachts, and ferries—helped ferry soldiers from shallow beaches to larger ships or directly back to England. Dunkirk 1940: Operation Dynamo
Vice Admiral Bertram Ramsay directed the mission from naval headquarters beneath Dover Castle . The operation was launched after German "Blitzkrieg" tactics
It was reportedly named after the room at Dover Castle that contained the building’s electric dynamo . Dunkirk 1940: Operation Dynamo