The German Army invaded in the West on 10 May 1940, by that time BEF consisted of 10 divisions, a tank brigade and a detachment of 500 aircraft from the RAF. During the Battle of France the speed of the German advance pushed them back, and after a brief armoured counterattack by the 5th and 50th Divisions, plus 74 tanks from the 1st Army Tank Brigade at Arras on 21 May, most of the BEF withdrew to Dunkirk. The evacuation began on 26 May, and over 330,000 British and French troops were withdrawn by 4 June. A further 220,000 were evacuated from other French ports. The majority of the BEF was saved, but had to leave much of its equipment behind. The BEF sustained around 68,000 casualties. This included around 40,000 who were taken prisoner, including most of the 51st (Highland) Infantry Division.