Northwest Europe: May 16-21, 1940 - Exploitation and Encirclement Phase
As highly mobile German armies surged into the open countryside west of the Meuse River in the center of the front the northern German armies attacked relentlessly, effectively tying down the Allied defenders on the Dyle River and preventing them from disengaging quickly to deal with the emerging threat to their southern flank. German panzer spearheads advanced over 30 miles per day. By May 20th, German tanks from the 2nd Panzer Division had crossed the Somme River and reached the English Channel at Abbeville. The German army had encircled approximately 1.7 million British, French, Dutch, and Belgian soldiers in an enormous pocket 120 miles long and 72 miles wide.
Map Courtesy of: Department of History, United States Military Academy