Order of battle
The naval order of battle for the operation consisted of two forces: Force 67, the strike force, and Force 69, the oiler group. The commander, Admiral Philip Vian, had his flag aboard the aircraft carrier HMS Indomitable (carrying 857, 1839 and 1844 Naval Air Squadrons). Also in Force 67 were the carrier Illustrious (carrying 854, 1830 and 1833 Naval Air Squadrons), the cruisers Argonaut, Black Prince and Newcastle, and the destroyers Kempenfelt, Wakeful, Wessex, Whirlwind and Wrangler. The oiler group comprised RFA Wave King and the destroyers Wager and Whelp.
The strike force departed from Trincomalee on 17 December, and met Force 69 the next day (18 December). Argonaut, Black Prince and the destroyers of Force 67 refuelled. Undetected, the fleet reached the flying-off position, north of Diamond Point, in the early morning of 20 December. The aerial order of battle consisted of a strike force and an escort force. For the former, Indomitable supplied twelve and Illustrious sixteen Grumman TBF Avengers, each with four 500-lb bombs, and Illustrious supplied a further four Vought F4U Corsairs, each with two 500-lb bombs. The strike leader was Lieutenant Commander W. Stuart. Among the escorts, top cover was provided by eight Grumman F6F Hellcats from Indomitable, middle cover by twelve Corsairs from Illustrious, and close cover by a further eight Hellcats from Indomitable.
Operation
At the flying-off position, low clouds and heavy squalls reduced visibility, prompting Vian to postpone the launch twenty minutes. The operation finally began at 0636. One of Indomitable′s Avengers crashed into the sea after takeoff, but its crew escaped unscathed. The other Avengers and the escort force departed from the fleet at 0715, and the strike Corsairs took off shortly after. The strike force ran into a barrier of clouds as they approached the Sumatran coast. Strike Leader Stuart advanced through a gap in the clouds to inspect the target but was unable to locate it. The strike was diverted to the secondary target, Belawan Deli, where the weather was little better.
The Avengers bombed the wharves from 1500 feet, while the Corsairs strafed the fuel storage tanks and warehouses in the town. A train was also hit at nearby Kuala Simpang. Two of the Corsairs became lost and strafed a large storage tank at either Pangkalan Brandan or Pangkalan Susu. The defences of Belawan Deli were unprepared: the anti-aircraft artillery was ineffective and no fighters were put in the air, although one Mitsubishi Ki-21 was surprised and downed by a Hellcat. The raid ended in chaos, with complete loss of radio discipline. The strike force and escorts rendezvoused just beneath the clouds. Lieutenant Commander W. J. Mainprice had to form up his squadron (No. 854) and lead them back on his own initiative because of the "radio bedlam". All 55 aircraft returned safely and the four Corsairs landed by 1050, and the force retired.
Aftermath
On the afternoon of the attack, a Japanese radio message was intercepted: "Am closing down now, will call you later." At the suggestion of Captain C. E. Lambe of Illustrious, eight of his Corsairs and eight Hellcats from Indomitable were dispatched for a low-level sweep over the airfields at Sabang and Oleelhoe, the port of Kota Raja. No Japanese aircraft were spotted, either on the ground or in the air. Force 67 had returned to Trincomalee by 22 December.
Despite the lack of opposition met, Operation Robson was considered a failure on account of the bad weather and the lack of radio discipline. The subsequent operations of Outflank—Lentil and Meridian—engendered a much greater response from the Japanese and concomitant British losses.
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HMS Illustrious was the lead ship of her class of aircraft carriers built for the Royal Navy before World War II. Her first assignment after completion and working up was with the Mediterranean Fleet, in which her aircraft's most notable achievement was sinking one Italian battleship and badly damaging two others during the Battle of Taranto in late 1940. Two months later the carrier was crippled by German dive bombers and was repaired in the United States. After sustaining damage on the voyage home in late 1941 by a collision with her sister ship Formidable, Illustrious was sent to the Indian Ocean in early 1942 to support the invasion of Vichy French Madagascar. After returning home in early 1943, the ship was given a lengthy refit and briefly assigned to the Home Fleet. She was transferred to Force H for the Battle of Salerno in mid-1943 and then rejoined the Eastern Fleet in the Indian Ocean at the beginning of 1944. Her aircraft attacked several targets in the Japanese-occupied Dutch East Indies over the following year before Illustrious was transferred to the newly formed British Pacific Fleet (BPF). The carrier participated in the early stages of the Battle of Okinawa until mechanical defects arising from accumulated battle damage became so severe she was ordered home early for repairs in May 1945.
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