Libya, North Africa. At 7.45 AM, Rommel's 5th Light Division attacks British 2nd Armoured Division at Mersa Brega, closely supported by Luftwaffe dive bombers. They are held by British anti-tank guns throughout the day. At 5.30 PM, German tanks and infantry advance through sand dunes by the seashore and enter Mersa Brega at 7 PM, but British tanks do not counterattack in the fading light. Under orders not to become heavily engaged with German tanks, the British withdraw 30 miles Northeast toward Agedabia overnight. British lose 60 men killed plus 8 armoured carriers and 1 anti-aircraft gun destroyed.
Eritrea, East Africa. British and Indian troops overcome Italian resistance on the road from Keren to Asmara (560 Italians taken prisoner). 5th Indian Infantry attack Italian defensive positions in a narrow valley at Adi Tekelezan, the last settlement before the Eritrean capital Asmara.
At 2.44 AM 125 miles South of Crete, Italian submarine Ambra sinks cruiser HMS Bonaventure escorting convoy GA8 from Greece to Alexandria, Egypt (138 killed, 310 survivors rescued by destroyers HMS Hereward and HMS Stuart). At 10.33 AM 300 miles East of the tip of Greenland, U-46 sinks Swedish tanker MV Castor carrying oil from USA to Sweden (all 15 crew lost). 28 miles Northwest of Messina, Sicily, British submarine HMS Rorqual torpedoes and sinks Italian submarine Pier Capponi (all 49 hands lost).
In the Red Sea, Italian destroyers Leone, Pantera and Tigre head North from Massawa, Eritrea, to attack British facilities at Port Sudan, Sudan. Leone founders on rocks off Massawa and is sunk by Pantera and Tigre, which then return to Massawa.