With the outbreak of war, 50 Division embarked for France on 14 September 1939 as part of the British Expeditionary Force. There, on 21 May 1940 during the Battle of France, Martel directed the tank attack on "Generalmajor" Erwin Rommel's 7th Panzer Division in the Battle of Arras in which the German frontline was driven back eight miles. The gains could not be held, but the Germans were forced to cease their offensive and regroup, so buying time for the BEF's evacuation from Dunkirk.