The success of the Allied landings in Normandy on 6 June 1944, and the subsequent campaign to liberate Europe, was dependant on preventing reinforcements being brought into Normandy from the Russian Front as well as other occupied territories such as Greece, Yugoslavia and Norway.

As the nearest part of Britain to Norway, it was inevitable that Scotland would play a large part in ensuring that German troops, tanks, aircraft and shipping based in Norway remained there. In order to achieve this aim, it was decided that German intelligence should be led to believe that the Allies were planning to invade Norway from Scotland. This deception operation, named Fortitude North, was co-ordinated from Edinburgh Castle and consisted of a number of different schemes which, put together, would give the impression of the assembling of a large invasion force training for a Scandinavian campaign.

It was vital that it should appear to the Germans that a large force was being assembled, at a time when all available troops were being trained and organised for the real invasion to take place in Normandy. It was therefore necessary that a few troops should appear to be many, and this required extensive and elaborate deception schemes.

These plans involved units across the whole of Scotland, but the East Lothian area had a particularly central part in the deception schemes. What shipping was available was anchored in the Firth of Forth, including the harbours at Dunbar and North Berwick, the numbers of vessels in the area rising from 26 at the beginning of April 1944, to 71 by the middle of May. By 'allowing' German reconnaissance aircraft to photograph the ships and barges, since the ack-ack gunners had orders to put up a barrage but that the aiming should be very poor, Luftwaffe photo interpretation experts were led to believe that a large invasion fleet was being assembled.

However, since it could not be guaranteed that weather conditions would be suitable for reconnaissance aircraft at the intended times, more emphasis in Fortitude North was placed on bogus radio signals than visual deception. Since the real radio messages of an invasion force could not be sent, small units were used to send out the equivalent number of signals of a whole army. It was this deception which was based in East Lothian, the units involved operating out of Macmerry aerodrome.

The 52nd Mountain Division was involved in an exercise conducted without troops, using radios in vehicles under the control of officers who had orders to maintain normal tactical wireless traffic throughout the period of the exercise. Correct radio procedure was followed and standard coding practice carried out. It was only after the end of the war that the troops involved found out exactly what the purpose of the exercise had been.

In early 1944 Nos. 2737, 2830 and 2949 Squadrons, Royal Air Force Regiment (see 13a and 13b) were sent to Macmerry where they received training in mountain warfare and were issued with equipment for such work - boots, tents. One of the squadrons was even given snow shoes. Although the squadrons were eventually sent to Norway, leaving Leith on 14 May 1945, the mountain training they received was part of the deception operations.

Several books have criticised Fortitude North, claiming that it was ineffective and failed to convince the Germans to send reinforcements to Norway. However, the German garrison in Norway was maintained at 12 divisions, and thus no troops were sent from Norway to the fighting in Normandy. The arrival of such units in the early weeks of the landings might have crucially tipped the balance against the Allies, and thus Fortitude North, and the radio deception work carried out from Macmerry, was of considerable importance to the success of the Allies in the Second World War.