It formed part of Operation Bodyguard, a broad strategic deception plan instigated by the Allies throughout the year to help cover the June 1944 invasion of Normandy.

It complemented efforts to deceive the Germans into believing that the Allies would also land in southern France at this time (Operation Vendetta).

Ironside intended to play on German fears of an invasion in the region, with the aim of tying down defensive forces following Operation Overlord in June 1944.

The invasion story was replaced with a supposed Allied plan to increase French resistance in the Bordeaux region to tie up German forces.

[5] Bordeaux was an important port for the German war effort, receiving a great deal of cargo, mostly raw materials, from overseas.

[7] In January 1944, the Allies intercepted communications indicating that German commanders were concerned by the possibility of landings in the Bay of Biscay region of France.

Newman Smith, based out of New York and responsible for the US elements of the deception, felt this was an unrealistic story and suggested a large force from the US might conceivably reinforce a bridgehead established by units from the UK.

[8][12] The lead was given to the less important Agent Bronx, a Peruvian socialite named Elvira Chaudoir, who communicated with her German handlers via letter.

[8][12] Agent Tate (a Dane sent to England in 1941 and turned double shortly after) opened the operation, on 23 May, in a message to his German handlers stating that a friend from the US had identified an expeditionary force, consisting of six divisions, preparing to sail.

[3] One of the most critical Bodyguard agents, Garbo, did become involved on 5 June, but only in forwarding the message of a fictional sub-agent who he had already identified as unreliable (MI5 hoped that this would cover for, in their opinion, the implausible nature of the story).

He identified the six divisions under Fredendall being sidelined for specialist training in bridge building but not amphibious assault and under heavy security.

Known to be under German control, when the operator asked about routes to send escaped prisoners of war the handlers replied that they should, from 15 June, be sent toward Bordeaux.

McIntyre quotes senior Allied figures, such as John Masterman (chair of the Twenty committee) and Hugh Astor (MI5), who attributed the delayed German response in part to Ironside.

[3] Part of the problem was that Bordeaux may not have appeared a plausible Allied target because it was out of range of fighter aircraft cover from the United Kingdom.

In common with other, higher-impact, Bodyguard deceptions it preyed on a concern that the Allies knew Hitler and the German High Command had discussed.

[14] John Bevan had asked Newman Smith to retain the threat of a US invasion force beyond 28 June when the initial deception was supposed to have ended.

It was decided that a new story would be presented to the Germans, suggesting that the Allies intended to bolster French resistance in the south of the country.