On the outbreak of the Second World War, the BEF took up defensive positions along the Franco-Belgian frontier. Under the command of General John Gort, the force included four regular infantry divisions and 50 light tanks.
By May 1940, one more regular and five more divisions from the Territorial Army had arrived. There were now 394,165 men in France with 237,319 assigned to front-line service. Tank strength had grown to a two-battalion infantry tank brigade (100 tanks) and two cavalry light tank brigades (200 tanks).
General Fedor von Bock and Army Group B attacked the BEF on 14th May, 1940. As Bock's men pushed the Allied forces back towards the French frontier, General Gerd von Rundstedt and Army Group A invaded France through the Ardennes. Rundstedt's offensive cut communications between French and British commands and left the BEF surrounded on three sides.
General John Gort attempted to halt the German Western Offensive by launching a counter-attack against the German Army at Arras. The attack on 21st May, 1940, could not be sustained and Gort decided to withdraw to Dunkirk so that his army could be evacuated to Britain.
Between 27th May and 4th June, 1940, a total of 693 ships (39 Destroyers, 36 Minesweepers, 77 trawlers, 26 Yachts and a variety of other small craft) brought back 338,226 people back to Britain. Most of these were members of the British Expeditionary Army but it also included 40,000 were members of the French Army. All the tanks and large guns had to be abandoned and left in France.