Operation Fortitude and the Double Cross System

Bodyguard and Fortitude

In July 1943 a secret group of officers, the London Controlling Section, began planning an operation codenamed Bodyguard. Its aim was to mislead the Germans about the timing and location of the Allied invasion of north-western Europe.¹

One of its main elements was Fortitude South: convincing the Germans that the invasion would come through the Pas-de-Calais. At its centre was the fictitious First United States Army Group (FUSAG), supposedly stationed in south-east England under General George Patton.^1,2

Dummy landing craft made of scaffolding, wood, canvas and empty barrels were deployed around Dover, and fake radio traffic simulating FUSAG’s communications was relayed from the tunnels of Dover Castle.¹

The UK National Archives holds a post-war account of the Fortitude plan as the deception plan for the Normandy invasion (CAB 106/1122, 1954).³

The Double Cross System

The double agents were run by MI5’s Twenty Committee, so called because the Roman numeral XX is a ‘double cross’. According to MI5, 120 German agents were turned during the war.^1,4

Intelligence from Ultra, the breaking of German communications at Bletchley Park, let the Allies check whether the Germans believed the falsehoods fed to them. MI5 credits the Bletchley codebreakers with providing indispensable support for the whole system.^1,4

GARBO

Juan Pujol was born in Barcelona in 1912. In 1941 he made three unsuccessful approaches to the British in Madrid and Lisbon. He then offered his services to German intelligence in Madrid, posing as a pro-Nazi Spanish official, and was accepted.²

Instead of going to England, he settled in Lisbon and began inventing a network of sub-agents. In April 1942 he reached MI6, was brought to London and taken over by MI5. His case officer was Tomás Harris.^2,5

Pujol and Harris wrote 315 letters to Madrid, averaging about 2,000 words each, and from August 1943 most reports went by radio. Between January 1944 and the Normandy landings more than 500 radio messages passed through Madrid to Berlin.²

He was helped by his wife, Araceli. MI5’s files also record her crisis in London and how it was resolved (KV 2/4190, 4192, 4195, 4200); a diagram of the GARBO network survives in WO 208/4374.⁵

June 1944: Normandy as a ‘diversion’

On 9 June 1944, three days after the landings, GARBO sent a long report asking that it be passed urgently to the High Command: Normandy was only a diversion ahead of the main blow at the Pas-de-Calais, since Patton’s army group had not moved from south-east England.²

According to MI5, throughout July and August 1944 the Germans kept two armoured and 19 infantry divisions in the Pas-de-Calais area. Churchill was informed that the Germans had intended to move certain divisions from the Pas-de-Calais area but had not done so.^2,4

On 29 July 1944 Hitler awarded GARBO the Iron Cross, and in December 1944 the Director General of MI5, Sir David Petrie, presented him with the MBE. Pujol died in Caracas in 1988.^2,4

The official history and research

The official history of British intelligence in the Second World War (the History of the Second World War series, HMSO) includes volume 3, part 2, by F. H. Hinsley and others (1988), and Michael Howard’s volume 5 on strategic deception (Strategic Deception, 1990).^6,7

In a peer-reviewed article in Intelligence and National Security (online since 2023), Jago Morrison uses the GARBO network to show that double-agent networks served not only for one-off disinformation before D-Day but for a sustained campaign that made the Germans believe successive plans and act on them; he also highlights the role of the writers working for MI5.⁸