Day 1085 August 20, 1942

Guadalcanal. Overnight, Japanese Colonel Ichiki moves his 770 troops forward to within a few miles of Henderson Field, stopping at 4.30 AM. Ichiki is still fooled by intelligence reports that a minimal American presence holds the airfield. However, after the clash of patrols at Koli Point yesterday, US Colonel Clifton Cates deploys 1st and 2nd battalions 1st Marine Regiment, plus two 37mm anti-tank guns loaded with canister shot, along the West bank of the Tenaru River (known as Alligator Creek to the Americans), while 75mm and 105mm artillery range their guns on the East side of Alligator Creek. In addition, US auxiliary carrier USS Long Island flies off 19 Grumman Wildcat fighters (VMF 223) and 12 Douglas Dauntless dive bombers (VMSB 232) to Henderson Field.

In the North Atlantic 250 miles West of the Faroe Islands, a US Catalina flying boat (squadron VP-73) catches U-464 (a supply U-boat on the first patrol) on the surface. At 5.30 AM, the Catalina drops 5 depth charges, badly damaging U-464 which can make 8 knots but not dive (2 killed). Icelandic trawler Skaftfellingur takes off 51 survivors and, at 8.15, U-464 is scuttled. At 8.45 AM, the survivors are turned over to British destroyer HMS Castleton.

Guadalcanal. In the evening, Colonel Ichiki moves forward to attack Henderson Field. At midnight, they are surprised to run into the US Marine defenses at Tenaru River (Alligator Creek).

Overnight, Luftwaffe bombers mount a small raid on Portsmouth on the South coast of England.