Monday April 27th 1942.
Joseph Rochefort's cryptanalytic team based in Pearl Harbor, US Territory of Hawaii reported that the Japanese Navy had changed call signs of some major warships, possibly indicating that a major operation was about to take place. They also noted a radio message from Nobutake Kondo to Tokyo, requesting navigation charts and latest intelligence around Dutch Harbor and Kodiak on the Aleutian Islands.
USS Yorktown departed Pearl Harbour bound for the Coral Sea.
Japanese aircraft attacked the airfield near Darwin, Australia; 3 Japanese bombers and 4 escorting fighters were shot down by the RAAF fighters assigned to the airfield, while the Australians lost 4 P-40 fighters.
9 Japanese Type 1 bombers and 11 Zero fighters attacked Seven Mile airfield near Port Moresby, Australian Papua, destroying 3 Hawker Henley and 1 Blenheim aircraft.
Following operation ‘Ice Pack’ against Soviet Naval vessels at Leningrad, 31 British Halifax and 12 Lancaster bombers, flying from RAF Vaenga, Murmansk attacked German positions to little effect.5 bombers were lost during this attack.
With the introduction of convoys from Britain to Casablanca, Admiral Dönitz issued a new order to his submarine commanders, instructing that they were to cross the Bay of Biscay submerged during the night and to resurface during the day only long enough to recharge their batteries. This proved something of a mistake for the Germans as it permitted some 12 RAF Squadrons to contribute to daylight anti-submarine operations.
During the months of March and April Royal Marines Viper Units harass Japanese lines of communications with ambushes and sabotage, as well as providing intelligence from deep behind enemy lines. The Commandoes of 8RMLI, 9RMLI, and 11RMLI, rotated a fortnight in the field, one week in the box, two weeks training and one week R&R after the field operations. were able to consolidate themselves in the wide area between Thailand and Japanese forces besieging Singapore and Penang Boxes and outposts were set up, standing patrols instituted and intelligence gathered and collated. All this information was relay back to Governor Sir Shelton Thomas, Admiral Sir Alban Thomas Buckley Curteis, Air Marshall Robert Brooke-Popham, and Lieutenant-General Arthur Percival at Singapore.
During the night the Luftwaffe aircraft conducted a raid on Norwich.
As dawn broke a large gathering of Free French warships at Mers-el-Kébir was spotted by German troops in the Foreign Legion. Though many had been rooted out of front line units, there were still several German nationals in rear units.
The French battleships Strasbourg, Dunerque, Richelieu; the light cruisers Duguay-Trouin, FR Lamotte-Piquet and FR Primauguet; the large destroyers Milan and Epervier; the destroyers Casque, Epee, Fleuret, Lansequenet, Le Corsaire, Le Flibustier, Le Hardi, Mameluk. Simon, Tornade, Trombe, Typhon, Minstral Tempete and Tramontane; the submarines Ceres, Iris, Le Conquerant, Le Tonnant, Meduse, Antiope, Minerva, Pallas, Le Heros and Le Glorieux, Venus and Junon. Also present were HMS Una, HMS Unbeaten, HMS Urge and HMS Ursula.
General Giraud, co-President of the Comité Français de Libération Nationale (French Committee of National Liberation) with General de Gaulle, the American Major General Mark Clark, Lt. Col. Magrin-Verneret, Lt. Col. Dmitri Amilakvari, Fred Scamaroni, and Paul Colonna d'Istria’s presences was also reported back German HQ.
Number 10 Free French Commando and 13th Demi-Brigade, composed of French Marine infantry, Senegalese Tirailleurs, North African spahis and a cavalry unit of Cherkesses were also gathering at Oran.