Operation Accumulator
By Jerry Proc VE3FAB


Researcher Roger Basford provides a former TOP SECRET document from the UK National Archive which summarizes the involvement of His Majesty's Canadian ships HAIDA and HURON in Operation Accumulator, on 12/13 June, 1944.

In slightly less than a week after D-Day, there was concern in Allied Command that the Germans might move troops stationed in the western part of the Cherbourg Peninsula [1] towards Utah and Omaha beaches at Normandy. In addition, it was hoped that a feint in the western part of the Cherbourg Peninsula would draw off part of the heavy German forces defending the valuable seaport at Cherbourg and thus facilitate its capture by the armies of liberation.

Early in the morning of June 13, 1944, HMC Ships HAIDA and HURON were tasked with the mission of creating bogus radio traffic in order to make the Germans believe that Allied troops would be landing on the west coast of the Cherbourg Peninsula. The diversionary sweep was developed and supported by the British Army.

accumulator1.jpg
A fake landing was to take place on the beaches near Granville. The map shows the relative position of Cherbourg and the Normandy Beaches to the phony attack site. (Map courtesy Google Maps)
This diversion was staged on extremely short notice. HAIDA and HURON were the only ships available for the task. The phony radio traffic would be most convincing if it represented urgent, last-minute rearrangement of plans and if it also looked like radio silence had been broken at sea.

A "script" was developed for HAIDA and HURON by the British 21 Army Group staff officers. Appropriate wireless sets (WS12 and WS22 sets) were borrowed from the Naval Mobile Deception Unit and flown to Plymouth where they were installed in the two destroyers. Operators were drawn from special (RN) naval radio deception units under the code name CLH.

Major Rooke of the 21 Army Unit,  together with a Leading Telegraphist from the Naval Deception Unit (NDU,) sailed in HAIDA. Rooke assumed the role of a  Brigade Commander. Sub Lt. Jones of NDU boarded HURON. The script was “cast” among the participants and rehearsed aboard HAIDA. Both vessels slipped their lines and sailed at 20:00 on June 12.

Due to lack of co-ordination with other services and units, an RAF reconnaissance aircraft from 19 Group sent a sighting report of two unidentified ships (HAIDA and HURON) and their positions at 2309.  At the time the report was made, the visibility was good so faulty ship recognition by this particular aircraft was to blame for the error. At 23:42, the aircraft reported that the two ships were friendly. There was lack of liaison between A.C.H.Q Plymouth and 19th Group. The report itself was made in Aircraft Reporting Code and fortunately there was no visible reaction on the part of the German military. This non-reaction by the Germans did however, instill confidence in the security of the Aircraft Reporting Code.This action might have alerted German radio monitors to something suspicious.

At 0150, Major Rooke reports that he is unable to get his WS-22 radios "netted" [2] correctly due to the short amount of available time. As a result, the script was hastily “recast” by Lt. Jones so that HURON could simulate both sets of signals.

Ahead of the planned flow of bogus traffic,  a message was transmitted to indicate a potential assault by ' Q ' division on the beach area north of Granville in the early hours of June 13. Next a message is sent to indicate a defective plummer bearing in the vessel carrying the assault troops of ' T ' battallion. The vessel must reduce its speed to 8 knots. As a result, it will alter the arrival time of the assault battalion. It is reported as an 'IMMEDIATE' message. In response, the commander of 'A' battalion breaks radio silence to respond to the message.

The transmission of bogus radio messages began at 0258 on June 13 and lasted until 0327. The result, as heard, was considered satisfactory. However, there was no reaction from the Germans. No forces were moved from the  port of Cherbourg or surrounding area. The mock landing was heralded by a heavy Allied air bombardment of the beaches and HAIDA's men watched with considerable interest, and  with some anxiety, the massive fireworks display bursting above the fiercely contested peninsula. The men agreed it was not exactly their "cup of tea" and no one was any the sadder when at last the order was given to clear the area and shape course for the more familiar mid-Channel waters where a destroyer had some searoom in the event of an encounter with enemy forces.

The green arrow indicates the position (48 58N, 03 45W) of Haida and Huron when first spotted by the reconnaissance aircraft from 19 Group at 23:09 hours on June 12.  (Map courtesy Google Maps)
FREQUENCIES USED

2300 KHz for ship to shore.
2640 KHz for the No.12 wireless sets. There was one each in Haida and Huron.
4115 KHz for the No.22 wireless sets. There were two each in Haida and Huron.

In total, there were six, scripted, multipart messages sent with appropriate responses within the alotted time window.  This involved the non-existent 'A',  'S' ,'T', and 'U' Battalions and 'Q' Division.

EQUIPMENT USED

ws12.jpg
Wireless Set No. 12 was developed in 1940 as a medium range, general purpose transmitter.  Frequency range is 1.2 to 17.5 MHz  and the RF power output was approximately 7 watts on AM and 25  watts  on CW. (Courtesy of "Wireless for the Warrior" web page)
Wireless Set No. 22 is a  portable transmitter/receiver developed in 1942 for general purpose, low power vehicle and ground station use.  Frequency range is 2  to 8 MHz. RF output approximately 1.5 watts.  Modes: R/T and CW. (Courtesy of "Wireless for the Warrior" web page)
FOOTNOTES:

[1] Also known as the Cotentin Peninsula.

[2] Netting is the process of tuning up two or more radios so they are all on the same receive and transmit frequencies.



Contributors and Credits:

1) Roger Basford  G3VKM  <Roger(at)new-gate.co.uk>
2) Operation Accumulator Report from the Officer-In-Charge, Mobile Deception Units.  Ref: CLH/A.134/44 dated 15 June, 1944.
3) "Haida...A Brief History" by historian E.C. Russell. Pg 23.
4) "Wireless for the Warrior" web page  http://wftw.nl/gallery/ws12.html
 
 

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April 30/13