'Dundas' was an Allied deception plan designed to persuade the Germans that the pace of the Allied build-up in the UK, especially of US forces, was greater than in fact it was (May/August 1943).
The necessity for convincing the Germans that Allied forces were strong enough to carry out operations of such magnitude as 'Starkey', 'Tindall' and 'Wadham', which were in themselves deceptions, brought home to the UK for the first time the need for order of battle deceptions of the type created in North Africa and the Mediterranean by Colonel Dudley W. Clarke’s 'A' Force organisation.
Separate projects were conducted for the US and British forces, carried out entirely through the double agents and known as 'Larkhall' and 'Dundas' respectively.
Schemed by the London Controlling Section, 'Dundas' was designed to create inflated estimation of British strength, but was run in a less satisfactory manner. Overestimating the German signals intelligence service, MI.5 feared that the double agent system would be blown unless reports of fictitious British divisions were confirmed by corresponding spurious radio traffic. However, neither personnel nor equipment sufficient for this task was available in 1943, so the Chief-of-Staff of the Supreme Allied Commander (COSSAC) organisation and MI.5 would not allow fictitious British divisions to be 'activated' for 'Dundas'. The deceiver teams had therefore to be content with the 'story' that British forces in the UK had been reorganised for an offensive role, with the former Expeditionary Force renamed, somewhat prophetically, as the 21st Army Group, composed of two British armies and one Canadian army; the Scottish Command and Eastern Command became the 4th Army and 6th Army respectively; and there emerged a Home Forces Static, under-equipped and intended largely for home defence.
By August, when the parallel 'Dundas' and 'Larkhall' ended, the Germans had been 'informed' that there were 570,000 US troops in the UK, whereas the actual number was 330,000.
The Germans had arrived at a greatly exaggerated estimate of Allied strength in the UK during 1943, though as usual it is hard to tell how much of that exaggeration resulted directly from the US 'Larkhall' and British 'Dundas' efforts. The Fremde Heere West army intelligence and assessment organisation estimated in October that there were 43 Allied divisions available for a landing in Scandinavia or North-West Europe. At the beginning of November, Generaloberst Alfred Jodl, the chief of the operations staff of the Oberkommando der Wehrmacht, gave a comparable estimate to an audience of Nazi local administrators in Munich, adding that the Allies possessed a sea lift capability to deliver an assault force of 11 or 12 infantry and one or two armoured divisions, as well as an air lift capability for 20,000 airborne troops.