This was a British sea and air radar deception designed specifically to persuade the Germans that an Allied invasion of the Pas de Calais or round Le Havre was imminent (5/6 June 1944).
The undertaking was part of the ‘Fortitude’ deception scheme, more specifically its 'Bodyguard' element, intended to provide protection for ‘Overlord’ by diverting German attention from the Normandy area, and involved the RAF’s No. 617 Squadron flying Avro Lancaster heavy bombers with its crew enlarged to 14 men, carrying the G-H radio navigation system, and adapted for the dropping of large quantities of ‘Window’ (chaff) over a small southbound ‘invasion’ convoy in the English Channel so that German radar operators would assess it as a large fleet moving toward the Pas de Calais or Le Havre at 7 kt on a 14-mile (22.5-km) front. The squadron started to train for its mission on 7 May, although the men were not told the precise details of the undertaking until a considerably later date.
Undertaken in parallel with 'Glimmer', 'Taxable' was the larger of the two operations, and was carried out by 18 small boats (a mix of Royal Navy harbour defence motor launches and RAF pinnaces also carrying G-H) designated as Special Task Force A.
Special Task Force A departed port during the evening of 5 June, but struggled in bad seas which affected their equipment and also their ability to converge at their rendezvous point. By 00.37 on 6 June the leading boats were on schedule and had reached the muster point. Between 02.00 and 04.00 the boats operated radar and radio equipment as they headed toward a point 7 miles (11.25 km) off the Cap d’Antifer. From there the task force simulated a landing attempt by running fast to within 2 miles (3.2 km) of the beach before returning to the 7-mile (11.25-km) marker under cover of smoke. During this time only a small German response was observed including searchlights and intermittent gunfire.
The operation ended shortly after 05.00 and the task force laid mines before heading toward Newhaven, reaching port by 12.00.