What was the codename of the operation that evacuated Allied troops from Dunkirk?

The operation that evacuated Allied troops from Dunkirk was codenamed Operation Dynamo.

The evacuation took place from 26 May to 4 June 1940, after German forces rapidly defeated or outflanked Allied armies in France and trapped British, French and Belgian troops around the northern port of Dunkirk. The operation was directed from the Dynamo Room beneath naval headquarters in Dover, which inspired its codename.

More than 338,000 Allied soldiers were rescued and carried across the English Channel. Royal Navy warships worked alongside hundreds of civilian vessels, later celebrated as the “little ships.” Troops embarked from Dunkirk’s harbour mole as well as the beaches, often under German air attack. French forces also fought delaying actions that helped keep the evacuation corridor open.

Operation Dynamo was a retreat, not an Allied victory in the conventional military sense: much equipment was abandoned and France fell soon afterward. Its survival value was enormous, however, because it preserved the core of Britain’s army for the continuing war.