D - Day naval deceptions Operations Taxable , Glimmer and Big Drum were tactical military deception s conducted on 6 June 1944 in support of the Allied landings in Normandy . The operations formed the naval component of Operation Bodyguard , a wider series of tactical and strategic deceptions surrounding the invasion . Small boats , along with aircraft from RAF Bomber Command , simulated invasion fleets approaching Cap d ' Antifer , Pas de Calais and Normandy . Glimmer and Taxable played on the German belief , amplified by Allied deception efforts over the preceding months , that the main invasion force would land in the Calais region . Big Drum was positioned on the western flank of the real invasion force to try and confuse German forces about the scale of the landings . These operations complemented Operation Titanic , which was intended to confuse the Germans about the D - Day airborne forces . It is unclear whether the operations were successful due to the complexity of their execution , poor weather and lack of response from German forces . It is possible they contributed to the overall confusion of D - Day as part of the wider Bodyguard plan . Background . Glimmer , Taxable and Big Drum were World War II deception operations . They were conducted as part of Operation Bodyguard , a broad strategic military deception intended to support the Allied invasion of German - occupied France in July 1944 . Bodyguard was designed to confuse the Axis high command as to Allied intentions during the lead - up to the invasion . The London Controlling Section ( LCS ) had spent some time convincing German commanders that the First United States Army Group ( FUSAG ) represented the bulk of the Allied invasion force . FUSAG , however , was entirely fictional – its existence fabricated through Operation Fortitude South . The Allied story for FUSAG was that the army group , based in south - east England , would invade the Pas de Calais region several weeks after a smaller diversionary landing in Normandy . As D - Day approached , the LCS moved on to planning tactical deceptions to help cover the progress of the real invasion forces . As well as naval operations , the LCS also planned operations involving paratroopers and ground deceptions . The latter would come into effect once landings were made but the former ( involving naval , air and special forces units ) were used to cover the approach of the true invasion fleet . In preparation for the coming landings , Allied scientists had worked on a number of techniques for obscuring the size and disposition of an invasion force . The German defences relied on the Seetakt radar system . Scientists from the Telecommunications Research Establishment discovered that the resolution of the Seetakt was about 520 yards . To deceive the radar system they proposed dropping clouds of aluminium foil ( chaff , then code named Window ) at two mile intervals . The clouds would appear as a continuous blip , similar to one created by an approaching fleet , on German screens . The Allies also repurposed radio equipment , code named Moonshine , to jam the Seetakt signal . Allied command decided that , rather than mask the approaching fleet , these measures would serve to alert German defenses . So it was decided to combine these techniques with small groups of boats to simulate an entire invasion fleet aimed at the Calais region . Allied planners proposed that small boats , towing large radar reflecting balloons ( code named Filbert ) and carrying both Moonshine jamming and standard wireless equipment ( for transmitting fake traffic ) , would advance toward the French coast under a cloud of Window . The chaff and other countermeasures would hide the small size of the naval force while wireless traffic would play on the FUSAG story to mislead the Germans into expecting a major landing . A third deceptive force , Operation Big Drum , would use radar countermeasures on the western flank of the true invasion fleet . This operation was intended to lend confusion as to the extent of the landings in Normandy . Glimmer and Taxable . Glimmer and Taxable were very similar operations . They were executed in the early hours of 6 June 1944 whilst the invasion fleet was approaching Normandy . Taxable simulated an invasion force approaching Cap d ' Antifer and Glimmer threatened Pas de Calais . By dropping chaff in progressive patterns , Royal Air Force bombers were able to create the illusion of a large fleet on coastal radar screens . Beneath the chaff small boats towed radar reflector balloons and simulated the radio traffic expected of a large fleet . Once drawn to the coast , it was planned that the RAF would attempt to contain the German forces in the region , and away from Normandy , by bombing bridges and roads . The operations required precise flying in elongated circuits with replacement aircraft having to merge in seamlessly to avoid tell - tale gaps . The bombers were staged at intervals parallel to the French coast . Once in position they would spend two and a half minutes flying toward the coast , dropping chaff at fifteen - second intervals . Then the aircraft would turn and head away from the coast for two minutes and ten seconds . By repeating this circuit , the wide cloud of chaff edged toward the coast just like a real sea - borne fleet . The aircraft had to be modified by cutting a hole in the nose to allow the large quantities of chaff to be dropped . The larger of the two operations , Taxable was carried out by 18 small boats , a mix of Harbour Defence Motor Launch es ( HDML ) and Search and Rescue Pinnaces , designated Special Task Force A . Chaff was dropped by Lancaster bombers from the famous No . 617 " Dam Busters " Squadron . Each aircraft carried an expanded crew of up to 14 . The squadron began training for the operation as early as 7 May , but were not aware of their final target . Task Force A left port in the evening of 5 June , but struggled in bad seas which affected their equipment and ability to converge at their meeting point . However , by 00 : 37 on 6 June the lead boats were on schedule and had reached the muster point . Between 02 : 00 and 04 : 00 the ships operated radar and radio equipment as they headed toward a point offshore . From there the task force simulated a landing attempt ; by running fast to within of the beach before returning to the 7 - mile marker under cover of smoke . During this time only a small German response was observed including searchlights and intermittent gunfire . Shortly after 05 : 00 the operation ended and the task force laid mines before heading toward Newhaven , reaching port by midday . The air operations for Glimmer were conducted by No . 218 " Gold Coast " Squadron under Wing Commander R . M . Fenwick - Wilson . The squadron , which flew Short Stirling bombers , was much smaller than No . 617 and so no relief aircraft were available . Instead each aircraft carried two pilots who rotated flying duties . The naval contingent , Special Task Force B under the command of Lieutenant Commander W . M . Rankin , consisted of 12 HDMLs equipped with jamming gear , radios and radar - reflecting balloons . The task force began jamming operations at approximately 01 : 00 followed by radio chatter around an hour later . Glimmer elicited more response from German forces than Taxable including reconnaissance planes sent to investigate the " fleet " . After completing their assignment ( which , unlike Taxable , did not include laying mines ) the ships returned to port , reaching their berths by 13 : 00 on D - Day . Big Drum . Big Drum was similar to the other D - Day naval deceptions , but without an airborne component . Task Force C consisted of four HDMLs whose job was to operate as a distraction on the western flank of the invasion . Attached to Force U ( the westernmost convoy of the invasion fleet ) , the plan originally called for the task force to operate radar jamming equipment as it approached the French coast , holding off shore until first light . However , after the Germans failed to respond the ships moved to within of the coast . No response , either in the air or on the shore , was observed and the convoy returned safely to Newhaven . Impact . Taxable , Glimmer and Big Drum were complicated in execution , requiring coordination of air and naval forces . Launched in poor weather conditions , Taxable did not appear to have the desired effect and failed to elicit any response from the Germans . The reaction to Glimmer was more encouraging . The attacks on the bomber squadrons indicated at least to the satisfaction of RAF Bomber Command that the Germans believed a genuine threat existed . There is no evidence that Big Drum elicited any specific response from the shore . According to historian Mary Barbier , the adverse conditions and complexity of the operations contributed to the limited enemy response . From intelligence intercepts it appears that German forces in the Pas de Calais region reported an invasion fleet . In addition there are reports of the decoys being fired on by shore batteries in that area . In an 11 June report on the operations , Lieutenant Commander Ian Cox ( who was in charge of deception units ) indicated that German forces had been convinced by the fake radio traffic . Intercepted dispatches from Hiroshi Ōshima , the Japanese ambassador to Germany , made reference to the naval deceptions . An 8 June dispatch referred to the Calais region and stated " an enemy squadron that had been operating there has now withdrawn " . Although disappointed not to have seen any " action " during the night of D - Day , and still unsure of their actual impact , the bomber crews felt proud of the operations . Squadron Leader Les Munro of No . 617 Squadron wrote , " I have always considered the operation in one sense to be the most important the squadron carried out in my time – not because [ of ] bad weather , nor because of any threat of enemy action and not measured by any visible results , but because of the very exacting requirements to which we had to fly and navigate " .