This was a British naval undertaking against the Japanese-occupied Andaman islands group in the Gulf of Bengal to divert Japanese attentions from the Solomon islands group just before the launch of ‘Watchtower’ (21 July/9 August 1942).
To this end dummy invasion convoys were sailed from ports on the eastern coast of India and from Ceylon in the direction of the Andaman islands group, and the associated Force ‘A’ naval element of Admiral Sir James Somerville’s Eastern Fleet included the battleship Warspite, fleet carriers Formidable and Illustrious, light cruisers Birmingham, Effingham, Mauritius and Free Dutch Jacob van Heemskerck of the 4th Cruiser Squadron, and destroyers Inconstant, Inconstant, Australian Nizam and Norman, and Free Dutch Van Galen.
From 21 to 25 July some of the ships made the initial passage from Kilindini on the coast of East Africa to Colombo in Ceylon. In order to be in a position to attack a Japanese cruiser force reported by the Free Dutch submarine O-23 on 29 July, the main force departed Colombo on 30 July, and other ships departed Vizagapatam, Madras and Trincomalee on 1 August to simulate the movement of three transport convoys. Japanese reconnaissance aircraft were initially permitted to spot the movements, and then on 2 August a Japanese flying boat was shot down by a Grumman Wildcat fighter operating from Formidable.
Somerville decided to terminate the operation after its operational objective had been achieved, especially as the ships were now required for the ‘Ironclad’ operation against Madagascar. Force ‘A’ therefore turned back, reaching Colombo on 3 August, and ‘Stab’ was declared to be at an end on 9 August.