Narvik, Norway. British, French, Polish & Norwegian forces attack across the Rombaksfjord from Oyord in landing craft and by land from the East and West. Naval bombardment of German positions begins at midnight, aided by the broad daylight at this latitude (it is dark at the same time at airfields further South, preventing Luftwaffe bombers taking off in response). French Foreign Legion comes ashore with 5 French light tanks at 12.15 AM. Luftwaffe arrives at 4.30 AM, forcing the Allied fleet to withdraw & damaging the command vessel cruiser Cairo with 2 bombs (10 killed, 7 wounded). Narvik is in Allied hands by midday after several hours of back & forth hand-to-hand fighting. http://ibiblio.org/hyperwar/UN/UK/UK-NWE-Norway/UK-NWE-Norway-13.html
Just after midnight, King Leopold III as Commander-in-Chief accepts Hitler’s terms and surrenders Belgian Army. He does not consult the Allies or the Belgian government and both hold him in strong contempt for his actions.
Dunkirk. While heavy fighting rages around the perimeter, 11,874 Allied troops are evacuated from Dunkirk harbour and another 5,930 from the beaches. A flotilla of British fishing boats and small pleasure craft arrives to assist in the rescue. The small boats are able to get into shallow water and ferry men out to the larger warships for the journey to England.
Seige of Lille. 40,000 French soldiers, the remainder of the once-mighty First Army, are surrounded at Lille by 7 German divisions (3 armoured divisions, including Rommel’s). They will fight a delaying action until May 31, while the evacuation of Dunkirk proceeds.
Near Abbeville, French Char B1 Bis tank 'Jeanne d'Arc' remains functional after 90 hits in 2 hours.
At 9.24 AM, U-37 sinks French liner SS Brazza 100 miles West of Cape Finisterre, Spain (79 crew & 300 passengers killed). 53 crew & 144 passengers are rescued by French gunboat Enseigne Henry and armed merchant cruiser HMS Cheshire. http://www.uboat.net/allies/merchants/ships/327.html