'Wadham' was an Allied deception plan, originally known as 'Blast' (ii), for a landing near Brest and Cap de la Hogue on the Brittany peninsula of German-occupied north-western France (July/8 September 1943).

The concept was part of 'Cockade', whose other elements were 'Harlequin', 'Starkey' and 'Tindal'. 'Cockade' was an Allied plan to tie German forces in France during 1943, with consequent benefits to the development of Allied operations in Italy and Soviet operations on the Eastern Front. 'Cockade' was planned by Lieutenant General F. E. Morgan and the COSSAC staff, and involved an amphibious feint toward France with the object of alerting the Germans and provoking a major air battle in which, it was hoped, the Allies would be able to secure a decisive tactical victory.

Of the four separate parts of 'Cockade', 'Wadham' was allotted to the US Army, which planned that Major General Leonard T. Gerow’s V Corps should be responsible for the threat against Brest and perhaps other port areas in Brittany, with the added aim of persuading the Germans that US Army strength in the UK was greater than it really was.

The 'story' promulgated in 'Wadham' was that a US force under the overall command of Lieutenant General Jacob L. Devers was to land in Brittany after German reserves in France had been drawn to the Pas de Calais area to oppose 'Starkey', which was purportedly to have been launched two weeks earlier. (In the earlier planning stages it had been anticipated that the opening of a US army headquarters in England would be announced, as urged first by Lieutenant General Frank M. Andrews, currently commanding the US forces in the European theatre of operations, and then by Devers, initially as an aid to deception, then phasing into the real planning for 'Overlord', but this idea was soon abandoned.) Gerow’s US V Corps of five divisions from southern England, based on the real corps headquarters but with largely notional forces, would be the supposed Task Force 'A' to come ashore near Morlaix on the beaches to the west of St Brion to attack Brest from the rear and seize it and the beaches to the mouth of the Odet river. Some days later, the V Corps would be followed by Task Force 'B', comprising Major General Roscoe B. Woodruff’s US VII Corps of seven divisions arriving by sea directly from ports on the eastern seaboard of the USA under escort of substantial US Navy forces. The VII Corps was to relieve the US V Corps on the southern portion of the front and exploit the success of the landing and establishment of a lodgement with an attack to the east in the area to the south of the road linking Brest and Rennes, seizing the portion of the Breton peninsula in its sector and pushing the German forces to the east of the line linking Nantes and Rennes.

Never very plausible, 'Wadham' was poorly handled in both England and the USA, and came at a time when the Joint Security Control organisation was only just starting to become effective. As an undertaking under the aegis of a directive issued by the Combined Chiefs-of-Staff, 'Wadham' should have been planned and executed under combined and joint procedures, and should have been assigned to Joint Security Control for advanced study and integration into the rest of 'Cockade'. There should have been directives from the Joint Chiefs-of-Staff covering the participation of naval and ground task forces, but in fact there were none. Instead, the distinctly limited resources of the ETOUSA (European Theater of Operations, United States Army) were employed, and this organisation appears to have been wholly ignorant of joint procedures and clearly was unaware of the fact that Joint Security Control even existed.

These and other factors meant that much of the operation’s desired, and indeed vitally necessary, degree of realism was thus lost, as was the staff training, including civil affairs planning, which should have resulted from going through a proper exercise. Much of 'Wadham' comprised rushed planning by staffs at corps and divisional levels, few of whose officers were aware that it was all just an exercise. This was true not only of the V Corps in England but of the VII Corps at Jacksonville, Florida. Its staff was enlarged, and arrangements were made for divisions to be assigned to it. Woodruff made a well publicised visit to England and on his return to the USA issued a press release declaring his opinion that 'the European fortress could be cracked wide open'.

Implementation of the plan was undertake from the middle of July, and was regularly updated. A detailed 'scenario' for 'Wadham' established the events which were to take place, their dates, the 'story' of each for German consumption, the date by which the Germans should know the story, and remarks. In July, 'Bigbob' inflatable dummy tank landing craft began to appear along the south-west coast of England and dummy North American P-51 Mustang and Republic P-47 Thunderbolt fighters, as well as gliders, began to appear in large numbers on airfields which had previously been quiet, and the genuine 'Jantzen' training exercise in South Wales was passed off as part of training for the Brittany attack.

By 12 August, it had been reported to Devers that special means steps on the US side of the Atlantic Ocean were substantially complete. Double agents had passed to the Germans information that Woodruff had visited England and had been called home hastily; that training activities on the east coast of the USA were being accelerated; that it was beginning to be clear that the principal task force for the coming invasion would sail directly from US east coast ports; that elements of Major General William C. Carey’s US 101^st Airborne Division were in the theatre; and that Woodruff had been designated to command an important task force on the US east coast.

It was well into August before VII Corps noticed that no one had seen fit to bring the US Navy into an operation which was supposed to involve a major convoy from the US east coast, and via the wrong channels a fictional Task Force 69 was created, under the command of Rear Admiral Alan G. Kirk, to escort and support the US VII Corps' convoy. This had a notional sailing date of 24 October, and a naval officer was then attached to VII Corps' headquarters.

Abruptly, on 8 September, it was announced that the operation had been cancelled.