Battle of Kharkov. German 14th and 16th Panzer Divisions (1st Panzer Army) continue cutting into the Southern side of the Izium salient. The rapid German advance forces the Soviets to evacuate forward airfields at Izyum and Petrovskaia, reducing effective air support for the ground forces. Luftwaffe aircraft exploit this ruthlessly, destroying 130 tanks and 500 other vehicles. Strangely, Soviet 21st and 23rd Tank Corps continue their offensive, pushing further West.
10 miles off Burgas on the Bulgarian Black Sea Coast, Soviet submarine ShCh-205 sinks Turkish merchant SS Duatepe with torpedoes and schooner Kaynardzha with the deck gun. Small Turkish ships are believed to be carrying war material to German forces in the Crimea and on the Northern shores of the Black Sea.
German cruiser Prinz Eugen arrives at Kiel, Germany, from Norway.
British submarine HMS Turbulent arrives in the Gulf of Sirte for her 5th patrol. At 5.10 AM 50 miles Northwest of Benghazi, Libya, HMS Turbulent sinks Italian SS Bolsena which has been ferrying supplies from Italy to Rommel in Libya.
U-162 concludes a successful patrol off the Northern coast of South America near Barbados (sinking 9 ships for 47,181 tons). At 2.10 AM, U-162 sinks Norwegian tanker MV Beth (now a British Royal Fleet Auxiliary) carrying 10,109 tons of fuel oil.
In the Caribbean. At 6.15 AM 25 miles Northwest of North Caicos, U-558 sinks Dutch SS Fauna. 125 miles South of Cape Frances, Cuba, U-125 sinks US tanker MV Mercury Sun at 6.06 AM and American SS William J. Salman at 9.50 PM.
In the Atlantic 460 miles East of Martinique, U-156 sinks American SS Quaker City at 10.18 AM (10 killed, 29 survivors drift in 4 lifeboats for 4 to 8 days and 1 man later dies of his injuries). From 6.52 PM until 7.39 next morning, U-156 hits British tanker MV San Eliseo with 4 torpedoes but fails to sink the tanker which sails on and arrives at Barbados on May 20 for temporary repairs (returned to service after permanent repairs in USA).
Following the disruption of the Japanese invasion of Port Moresby, Papua, by the Battle of the Coral Sea, both Japan and the Allies move to secure Port Moresby. Australian 14th Militia Brigade moves there from Australia, while Japanese plan an overland attack from the North shore across the Owen Stanley mountain range.