when did the british expeditionary force go to france
British Expeditionary Force (World War II) The BEF (General Lord Gort) began moving to France in September 1939. The British assembled along the Belgian–French border on the left of the French First Army as part of the French 1er groupe d'armées (1st Army Group) of the Front du Nord-est (North-Eastern Front). Most of the BEF spent the Phoney War digging field defences on the French–Belgian border, before the Battle of France (Fall Gelb) began on 10 May 1940. The BEF constituted 10 percent of the Allied forces on the Western Front. The BEF participated in the Dyle Plan, a rapid advance into Belgium to the line of the river Dyle but had to retreat through Belgium and north-western France with the rest of the 1er groupe d'armées, after the German breakthrough further south at the Battle of Sedan. The BEF, French and Belgian forces cut off north of the Somme river were evacuated from the French North Sea coast through port and beaches of Dunkirk in Operation Dynamo.