Operation Quicksilver (deception plan)

Quicksilver was a World War II deception operation conducted mainly by the British (who were responsible for Plan FORTITUDE) but with input from the United States, Canada, and other Allied Nations. It was a very large military operation consisting of numerous sub-operations along the entire length of the English Channel, under the control of Lieutenant-Colonel David Strangeways the head of G(R), the deception section of General Montgomery's 21st Army Group.

Its purpose was to enhance enemy perception of the reality of the main plan of Allied deception, Fortitude South, the Fortitude sub-plan calling for the fabrication of a non-existent field army in the east and south-east of England, with the aim of threatening an invasion in the Pas de Calais region of France.[1]

Fortitude had evolved from plans submitted in the summer of 1943 by COSSAC, the predecessor-body of Supreme Allied Headquarters SHAEF in consultation with John Bevan of the London Controlling Section. Early revisions in January 1944 suggested a fictional build-up of troops in southern England with the hope of drawing German attention to the Calais region.[2] The final COSSAC/SHAEF plan was submitted by Lieutenant-Colonel Noel Wild, the head of SHAEF's deception section, Operations 'B'. Strangeways was unimpressed with Wild's approach. Having worked under Dudley Clarke in Cairo earlier in the war, he had learned Clarke's maxim that deception relied on getting the enemy to do something, not just think something.[3][4] Strangeways was widely critical of the original plan and by February, 1944, he had re-written the tactical threat with a harder, sharper focus on the Calais region.

The Allied story for FUSAG was that the army group, based in the south-east and east of England, would invade the Pas de Calais region several weeks after a smaller diversionary landing in Normandy. The order of battle for the army was intended to represent, from the German viewpoint, the bulk of Allied forces in England. Quicksilver was the code name for a number of deceptions to support the fabrication of FUSAG, including wireless deception, troop movements and bombing campaigns.[5]

Insignia of FUSAG, the fictional field army used during the operation

Strangeways' skeleton outlines of Quicksilver show that it consisted of six sections focused on the creation of the First United States Army Group (FUSAG).[6]:

1. Quicksilver I was the basic "story" for Fortitude: the First United States Army Group was to land in Pas-de-Calais after German reserves were committed to Normandy.[7]
2. Quicksilver II was the radio deception plan of Quicksilver, involving the apparent movement of units from their true locations to eastern and southeastern England.[8]
3. Quicksilver III was the display of dummy landing craft, including associated simulated wireless traffic and signing of roads and special areas.[9] The landing craft, built from wood and canvas and nicknamed Bigbobs, suffered from being too light. Wind and rain flipped many over or ran them aground.[10]
4. Quicksilver IV was the air plan for Quicksilver, including bombing of the Pas-de-Calais beach area and tactical railway bombing immediately before D-Day.[11]
5. Quicksilver V was increased activity around Dover (giving impression of extra tunneling, additional wireless stations), to suggest embarkation preparations.[12]
6. Quicksilver VI was night lighting to simulate activity at night where dummy landing craft were situated.

The operation was carried out mainly by means of false radio signals purporting to show units massing in eastern and southeastern England, together with false reports to German intelligence by double agents provided by the Double Cross System. Allowing one of the double agents to claim to have stolen documents describing the closely guarded invasion plans might have aroused suspicion. Instead, agents were allowed to report minutiae such as insignia on soldiers' uniforms and unit markings on vehicles. The observations in the south-central areas largely gave accurate information about the units located there: the actual invasion forces. Reports from southwest England indicated few troop sightings, when in reality many units were housed there. Reports from the southeast depicted the real and the notional Quicksilver forces. Any military planner would know that to mount a massive invasion of Europe from England, Allied units had to be staged around the country, with those that would land first nearest to the invasion point.

German intelligence used the agent reports to construct an order of battle for the Allied forces that placed the center of gravity of the invasion force opposite Pas de Calais, the point on the French coast closest to England and therefore a likely invasion site. The deception was so effective that the Germans kept 15 reserve divisions near Calais even after the invasion had begun at Normandy, lest it prove to be a diversion from the "real" invasion at Calais.[13][14]

Contrary to a widespread misconception, the FUSAG deception was not primarily implemented with dummy tanks, airplanes, landing-craft, or other dummy equipment. It relied mainly on deception via wireless-telegraphy. The explanation usually given for Quicksilver's comparative lack of visual or "physical" deception is that at that stage of the war it would have been a wasted effort, since Allied air dominance made it impossible for the Germans to fly reconnaissance planes over England. But though enemy air reconnaissance was less than originally expected, it is not the case that it ever died out completely. This explanation also discounts the principle that Strangeways incorporated in Quicksilver and called "Craft Indication", his strong belief that the enemy would use air reconnaissance of Allied concentrations of landing-craft as indicators of when and where the Allied invasion would be likely to strike.

In fact, the Germans continued to rely on air reconnaissance as a main means of gathering intelligence on Allied plans and confirming intelligence reaching them from the double-agents and other sources. Because they remained dependent on it as an intelligence source, the Allied deceptionists remained dependent on it too, as a means of getting across the "necessary false picture" of what the Allies were really planning. By the spring of 1944, in response to Allied air dominance, the Germans had evolved a new technique of oblique air surveillance of the Allied build-up of ships and landing-craft on the Channel coast. Strangeways adapted his use of physical deception accordingly.

This is not reflected in his outlines of the Quicksilver threat. Nor do the six published parts of the threat make any mention of the extensive use of physical deception around the enormous "dress rehearsals" for the invasion, exercises Tiger and Fabius held between April 26th and the first week of May, 1944.

In a recent book, "The Cover Plan Conspiracy", Nigel Lewis shows that the British Channel defences were lowered to allow an enemy air reconnaissance of the First US Army exercise, Tiger, on the morning of April 26th. This reconnaissance was falsified in the records, and altogether omitted from other records. The Americans knew nothing about it. It was the intelligence basis for the German torpedo-boat sortie on the night of April 27th/28th, which attacked the final, "follow-up" convoy of Tiger, Convoy T-4, with the loss of 639 American lives.

Lewis argues that the exposure of Tiger leading to the enemy attack on it was part of a hitherto unknown "western dimension" to the tactical threat of Fortitude South, designed to create the impression of an Allied feint, false feint, or diversion on the coast of Brittany. This was seen as necessary because the large concentrations of US amphibious forces in and around Plymouth Command at the western end of the English Channel were visible to enemy air reconnaissance and were so obviously inconsistent with the notion of an Allied invasion at the other, eastern end of the Channel, around Calais.

Like a southpaw boxer who reflexively lowers his right fist when landing a "killer punch" with his left, the guard around Plymouth had to be lowered for the threat to be credible. This was in keeping with the known Fortitude South policy of maintaining an appearance of overwhelming strength in the east of the Channel, and weakness in the west.

In this view, the dead of Convoy T-4 were not victims of an accidental "training disaster", as is routinely claimed, but collateral victims of the Fortitude South deception and, in particular, of its tactical threat, Quicksilver. Tiger was a case of physical deception and intentional "Craft Indication" making use of real ships, landing-craft, and men. The true cause of the T-4 incident was hidden in 1944, and it has been hidden ever since.

• "The Cover Plan Conspiracy: the British and Exercise Tiger, 1944" - Kindle e-book.
• "Decoy Army Fooled Nazi Masterminds", February 1946, Popular Mechanics