At midnight, U-107 stops Dutch tanker MV Marisa with a torpedo after following her for 12 hours (2 killed, 47 crew abandon ship in 3 lifeboats). U-107 sinks MV Marisa with the deck gun and antiaircraft gun but both guns are damaged when rounds explode in the barrel.
At 1 AM, Australian destroyer HMAS Vampire delivers fresh Australian troops to Tobruk, including 2/12th Field Regiment which is immediately pressed into action at 5.30 AM to support a failed probing attack on the German salient. This is the first time Australian artillery supports Australian infantry at Tobruk.
German invasion of Crete is delayed until May 20 by the late arrival in Southern Greece of tanker Rondine with 5,000 tons of aviation fuel.
At 5.30 PM, after 5 hours of negotiation, Duke of Aosta (Viceroy of Italian East Africa) agrees to a “surrender with honour” of the mountain fortress at Amba Alagi, Ethiopia. His troops will be allowed to march out with their rifles (to be surrendered later). In exchange, they will leave all artillery, weapons and stores intact and identify the location of all mines.
Iraq. Kingcol, the British mobile column from Palestine, arrives at Habbaniya late the evening. Overnight, elements of the Gurkha battalion, a company of RAF Assyrian Levies, RAF Armoured Cars towing captured Iraqi howitzers cross the River Euphrates using improvised cable ferries to advance 10 miles East on the town of Falluja.