The 'Cypris Defence Plan' was the British deception plan, after the German seizure of Crete in 'Merkur' (i), to suggest that Cyprus, which could have been Germany’s next target for airborne assault and whose seizure would have offered the Axis powers considerable strategic advantages, was held by forces considerable stronger than they actually were (7 June 1941 onward).
On 7 June, while in Jerusalem, Lieutenant Colonel Dudley W. Clarke, head of the Middle East Command’s fledgling deception apparatus, received from General Sir Archibald Wavell, the commander-in-chief, Middle East, an order that as the Allies had lost Greece and Crete, and therefore that there was now a major fear that Cyprus might be the next German objective, Clarke was to create a plan to delay any such attack for two weeks while reinforcements were sent to the island. Clarke prepared what was simply known as the 'Cyprus Defence Plan', and this proved to the first real long-term order of battle deception.
In his plan, Clarke set out to represent to the Axis powers that the British garrison of Cyprus was not the actual 4,000 British troops but rather something in the order of 20,000 men, representing one full division as well as local forces. On 13 June orders went issued for the redesignation of the command on Cyprus as the fictitious 7th Division, and for the brigadier commanding on the island to assume the rank of major general. A false headquarters establishment was created on the island, buildings were requisitioned, and misleading signs were placed. At the same time, rumours were started in both Egypt and Palestine, faked orders were circulated, and similarly fake military and civil telegrams simulated a high flow of orders and requests between Cyprus and the mainland. One squadron of dummy tanks was despatched to Cyprus, and a false defence plan of Cyprus, complete with maps and order of battle, was planted, in a 'haversack ruse', on an Egyptian woman known to be in touch with Japanese intelligence and a German female agent.
While the Germans never actually intended to attempt the seizure of Cyprus, the plan fixed in their minds the suggestion that the island was held by one or two divisions with more than 20,000 men: this was confirmed by documents captured early in July and confirmed by a report that the German military attaché in Turkey had indicated that Cyprus was more strongly defended than Crete had been. All this was confirmed by the capture, six months later, of an Italian intelligence bulletin containing a map of Cyprus with all the chief features of the 'haversack ruse' documents, further embellishment, and a troop estimate of some 30,000 men.
By the middle of July, Cyprus had been reinforced by a real formation, namely Major General W. H. C. Ramsden’s 50th Division. However, as it had already gained something of a life of its own in the 'Cyprus Defence Plan', the fictitious 7th Division was allowed to remain in existence, and to 'normalise' the presence of two divisions a fictitious headquarters on Cyprus was added as the fictitious XVIII (later XXV) Corps. This fake order of battle was continued, under several names, over the next three years. Captured documents and later 'Ultra' decrypts of Axis signals combined to reveal that throughout the period the Axis powers accepted the false order of battle without question.
It was around this nucleus that Clarke’s great accomplishment in strategic deception, namely the long-term false order of battle, came into being.