Operation Robson (20 December 1944) was the first of a series of aerial operations, Operation Outflank, undertaken by the British Pacific Fleet (BPF) against the oil refineries of Japanese-occupied Sumatra during World War II. Admiral Chester Nimitz, Commander in Chief, Pacific Ocean Areas, proposed a strike on the refineries to Admiral Bruce Fraser, commander of the BPF, during a meeting in early December. The primary target of Operation Robson was the refinery at Pangkalan Brandan. It had been fired by fleeing American and Dutch personnel during the invasion of the Dutch East Indies in 1942, but the Japanese had repaired it by the year's end. Refined product was piped from there to the port of Pangkalan Susu eight miles away and to the more distant deep-water port of Belawan Deli, the secondary target. Pangkalan Soesoe had tanks capable of holding thirty million gallons. 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 (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 , and , and the destroyers , , , and . The oiler group comprised RFA Wave King and the destroyers and . 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