Solomon Islands. On Guadalcanal, by 4 PM, US Marines capture Lunga Point airfield unopposed (named Henderson Field after Marine Major Lofton Henderson, who was killed in the Battle of Midway). On Tulagi, after hand-to-hand fighting overnight, US Marines advance on Hill 281 in the morning under a mortar barrage and wipe out Japanese troops in caves using dynamite. 307 Japanese are killed, in a fight to the death that will become familiar to US Marines, and only 3 are taken prisoner (45 US Marines killed). At Gavutu-Tanambogo, US dive bombers and warships pound Tanambogo before Marines land at 4.30 PM and overrun the defenders (476 Japanese killed and 20, mostly Korean labourers, taken prisoner; 70 Americans killed). Japanese aircraft from Rabaul, New Britain, attack US warships throughout the day. Troop transport USS George F. Elliot is set ablaze by a crashing dive bomber and destroyer USS Jarvis is badly damaged by a torpedo bomber (14 crew killed).
At 8 PM 14 miles West of Cape St. George, New Britain, US submarine USS S-38 sinks Japanese troop transport Meiyo Maru, killing 31 crew and 342 troops who are being brought to Rabaul to reinforce Guadalcanal.
However, the Japanese naval response is swift. In the morning, 7 cruisers and a destroyer depart base at Kavieng and Rabaul under Admiral Gunichi Mikawa. All day they steam down New Georgia Sound (known as "The Slot") through the Solomon Islands, evading detection. Overnight, the Japanese execute a night attack, catching the Allied warships napping at anchor off Guadalcanal and sinking 3 American cruisers USS Vincennes, USS Astoria, USS Quincy and Australian cruiser HMAS Canberra (1,077 killed).
Kokoda Track, Papua. Between 6.30 and 8 AM, 3 Companies of Australian 39th Battalion leave Deniki separately to retake Kokoda. Company A reoccupies the airfield, which is lightly defended, but the other Companies run into large Japanese forces and are repelled.
US submarine USS Narwhal sinks Japanese crab fishing boat Bifuku Maru 5 miles off the Northeast tip of Honshu, Japan. At the Southern end of Honshu, US submarine USS Silversides sinks Japanese freighter Nikkei Maru.
U-174, U-176, U-256, U-438, U-660 and U-705 reinforce the wolfpack attacking convoy SC 94, 485 miles Southeast of the tip of Greenland. Convoy escorts hold off all approaches until midday when U-176 and U-379 attack simultaneously and sink 5 ships. Crews of 3 freighters panic and abandon ship without reason. U-379 is sunk by ramming and depth charges from the British corvette HMS Dianthus (40 killed, 5 survivors).
Operation Pastorius. The 6 convicted German saboteurs are executed in the electric chair. President Roosevelt spares the informants George Dasch (given 30 years) and Ernst Burger (life sentence) whose actions had foiled the operation. In 1948, President Truman will free (but not pardon) Dasch and Burger and deport them to the American Zone of occupied Germany.
British submarine HMS Turbulent destroys the hulk of Italian destroyer Strale which ran aground off Cape Bon, Tunisia on June 21 after an attack by British FAA Swordfish torpedo bombers. In the Aegean Sea, South of Naxos, British submarine HMS Proteus sinks Greek sailboat Firesia.
Italian submarine Morosini goes missing in the Bay of Biscay (all hands lost).