'Rayon' was a British deception operation in the Mediterranean, based on the 'story' of an imminent invasion of Crete, and was designed to cover the passage of a convoy to Malta and also to prevent the Germans moving more forces from Crete to supplement those already in North Africa (July/September 1942).
The origins of the basic concept for 'Rayon' can be found in the period after the Japanese 'Ai' attack on Pearl Harbor in the Hawaiian islands group, precipitating the USA into World War I and raising great fears in Australia that Japanese would land forces on the continent’s north-east coast. As a result Australian land forces were recalled from the Middle East and Western Desert, and operational cover for this redeployment was provided by the small-scale 'Anagram' operation created by Colonel Dudley W. Clarke’s 'A' Force deception organisation in the Middle East. This undertaking managed to persuade Axis intelligence that the conspicuous preparations for that movement were in fact preparations for an invasion of the island of Crete. There seemed to be good evidence that the Germans believed this ploy, for they did indeed reinforce their garrison on Crete, and it therefore seemed worthwhile to play on the Germans concerns once again.
Late in July, therefore, 'A' Force launched 'Rayon' as a more elaborate threat to Crete with the shorter-term object of distracting the attentions of the Axis forces from the passage of the vital 'Pedestal' convoy to Malta, and the longer-term object of discouraging Axis reinforcement of their forces in North Africa from area of Greece in general and Crete in particular.
The 'story' promulgated by 'Rayon' was that the British were planning to launch a combined seaborne and airborne operation against Crete in the middle of August, using British and Greek troops, British ships and US air strength from bases on the island of Cyprus. The emphasis in the 'story' on the use of Greek troops and US air power was designed to avoid any suggestion that significant British forces might be withdrawn from General Sir Henry Maitland Wilson’s British 9th Army in the Middle East and General Sir Claude Auchinleck’s (from 13 August Lieutenant General B. L. Montgomery’s) British 8th Army in the Western Desert.
The false intelligence aspect of 'Rayon' had to be supported by physical measures because Axis reconnaissance aircraft regularly overflew Egypt as far to the east as the Suez Canal. New equipment, including 'Drybob' and 'Wetbob' dummy landing craft were used for the first time, while dummy gliders were used to suggest preparations for an airborne assault. Greek troops accompanied by a Greek destroyer were cycled through real amphibious training, and US aircraft in Cyprus undertook conspicuous activities. The intelligence implementation was focused on the dissemination of rumours in the large Greek community in the Middle East, and the use of a double agent.
The Malta convoy got through with losses which were severe but less disastrous than those of the preceding 'Harpoon'. 'Rayon' was then continued into late August and early September with a view to delaying the advance of the German and Italian forces deeper into western Egypt, and thus buy time for the 8th Army to increase its defences. 'Rayon' also paved the way for 'Treatment'.