British Expeditionary Force (WWII)

British Expeditionary Force (World War II)
The British Army in France, 1939
Active	1938–1940
Country	Britain
Branch	Army
Type	Expeditionary Force
Role	Field operations in France and the Low Countries
Size	13 divisions (maximum)
Part of	1er groupe d'armées (1st Army Group) Front du Nord-est (North-Eastern Front)
Disbanded	1940
Commanders
Notable commanders	Field Marshal Lord Gort Lieutenant-General Alan Brook

The British Expeditionary Force (BEF) was the name of the British Army in Western Europe from 1939 to 1940, in the early stages of the Second World War. During the 1930s, the British government planned to deter war by rearming from the very low level of readiness of the early 30s and abolished the Ten Year Rule. The bulk of the extra money went to the Royal Navy and the Royal Air Force but plans were made to re-equip a small number of Army and Territorial divisions, potentially for service overseas.

The BEF had been established in 1938, in readiness for war, after Nazi Germany annexed Austria in the Anschluss of March 1938 and made claims on Sudetenland in Czechoslovakia, that led to the Munich Agreement (30 September 1938), ceding Sudetenland to Germany and the German occupation of Czechoslovakia (15 March 1939). After the French and British governments had promised to defend Poland, the German invasion of Poland began on 1 September and on 3 September, after the expiry of an ultimatum, the British and French declared war on Germany.

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 1 er groupe d'armées, after the German breakthrough further south at the Battle of Sedan. The BEF, French and Belgian forces were evacuated from Dunkirk on the French North Sea coast in Operation Dynamo.