'Outflank' was a British carrierborne air attack on Japanese military installations and oil facilities at Belawan Deli on the island of Sumatra in the Japanese-occupied Netherlands East Indies (17/23 November 1944).
Under the command of Rear Admiral Sir Philip Vian, recently arrived in the theatre to assume command of the aircraft carrier force of Admiral Sir Bruce Fraser’s East Indies Fleet in succession to Rear Admiral C. Moody, a task force comprising the fleet carriers Illustrious and Indomitable, the light cruiser Newcastle, the light anti-aircraft cruisers Argonaut and Black Prince, and the destroyers Kempenfelt, Wakeful, Wessex, Whirlwind and Wrangler departed Trincomalee in Ceylon on 17 November.
After replenishing from the oiler Wave King, together with the destroyers Wager and Whelp, on 18 November, the carriers launched 27 Grumman Avenger bombers and 28 Vought Corsair and Grumman Hellcat fighters early on 20 November to attack Pangkalan Brandan in the north-western part of Sumatra. However, the deterioration of the weather compelled the attack force to divert farther to the south in the direction of its secondary target, the oil installations of Belawan Deli. Here the attacking aircraft were further were hampered by low cloud and squalls, and the attack therefore caused only modest damage to the port facilities. During the afternoon the aircraft attacked airfields near Sabang.
There were no British losses, and the task force returned to Ceylon on 23 November.