By 21 May the Allied armies were encircled and counterattacks had been repulsed at Arras. The Allies were evacuating the ports of Dunkirk and Calais. During the Battle of Dunkirk and Siege of Calais (1940), Richthofen supported the advance of Army Groups A and B in these operations. His command were frequently meeting Royal Air Force (RAF) fighters, flying across the Channel. Richthofen noted RAF Fighter Command and its No. 11 Group RAF were responsible for 25 per cent of German losses. Richthofen helped capture Calais and was awarded the Knight's Cross of the Iron Cross on 23 May. Richthofen was ordered to support the German Fourth Army, though he showed little interest in the Dunkirk battles. He regarded them as a waste of time, and they disrupted preparations against southern France (Case Red). He believed the attempt to destroy Allied forces, or prevent the evacuation with the Luftwaffe was unrealistic. Over Dunkirk, losses were heavy and progress slow. On 26 May, Richthofen made a special effort to gain and hold air superiority. Overall, German air power failed to prevent the evacuation.