'Quicksilver' (ii) was an Allied major component of the 'Fortitude South' deception plan designed to persuade the Germans to hold troops some distance away from Normandy in belief that the 'Neptune' (iii) landings was only a feint and that the major invasion was still to come in the Pas de Calais region (spring/summer 1944).

The key element of 'Quicksilver' (ii) was the creation in German minds of a fictitious US 1^st Army Group commanded by Lieutenant General George S. Patton, and the success of 'Quicksilver' (ii) is attested by the fact that for a fortnight after the launch of 'Neptune' (iii) and 'Overlord' on 6 June 1944, the German high command still believed that the Normandy operation was just a feint designed to draw major German forces away from the location of the 'real' invasion which, in accordance with established US military doctrine demanding the shortest and most direct assault on an enemy’s homeland, would therefore inevitably arrive on the coast of the Pas de Calais.

As finalised, 'Quicksilver' (ii) comprised a series of six sub-plans. 'Quicksilver I' was the basic 'story' for 'Fortitude South', detailing how the '1^st Army Group', supported by Lieutenant General Lewis H. Brereton’s US 9^th AAF, would embark at the ports of south-eastern England and descend on the Pas de Calais after the German reserves had been committed to Normandy. 'Quicksilver II' was the radio deception plan of 'Quicksilver' (ii), and designed indicate the 'movement' of formations from their true locations to south-eastern England. 'Quicksilver III' was the display of dummy landing craft, including associated simulated wireless traffic and signing of roads and special areas. 'Quicksilver IV' was the air plan, including tactical bombing of the Pas de Calais’s beach areas and railways immediately before D-Day. 'Quicksilver V' was increased activity around Dover to create the impression of extra tunnelling and the creation of additional wireless stations, so suggesting embarkation preparations. 'Quicksilver VI' was night lighting to simulate activity in port areas where dummy landing craft were situated.

Like the rest of 'Fortitude South', 'Quicksilver' (ii) was devised by and carried out under the supervision of Colonel David Strangeways, the deception officer of General Sir Bernard Montgomery’s Allied 21^st Army Group tasked with the implementation of 'Neptune' (iii) and 'Overlord'. The operation was carried out entirely by means of false radio signals purporting to show units massing in south-east England, together with false reports to German intelligence by double agents.