It was, of course, essential to paralyse the radar cover on the western front which the enemy had, with great thoroughness, established from Norway to the Spanish border. The closest concentration of radar stations was in north-west France and in the Low Countries. The system he followed was similar to that brought to so high a state of efficiency in Great Britain and was made up of a coastal chain supported by a number of inland stations. Between Dunkirk and Brest there were sixty-six radar stations of various kinds. To attack them all, even with the formidable air strength available to the Allies, was hardly possible and it was therefore decided to combine assault by air with radio counter-measures. The staff for this purpose was set up on 15th May under the direction of Air Vice-Marshal V. H. Tait, Director of Signals in the Air Ministry. They gave advice to the Naval and Air Commanders-in-Chief on everything connected with radio counter-measures and one of their chief duties was the choice of targets most suitable for direct air attack. Installations able to report on the movement of shipping or used to control the fire of batteries, or set up in areas where they might interfere with the landing of our airborne forces, were the most suitable targets. As a further precaution, for every radar post attacked in the lodgment areas two were attacked outside them. The attacks were postponed as long as possible so that the enemy should not be able to improvise equipment to cover the gaps in the radar chain which might be created. They did not, therefore, begin until 10th May, when the aircraft reporting stations were bombed. These installations if hit, could not be easily repaired, and because of the narrowness of their beam were hard to jam. A week later the attacks on night fighter control stations and on the stations controlling the fire of coastal batteries were begun. During the week before 'D Day', a series of attacks on forty-two radar sites, most of them provided with more than one type of equipment, was carried out, and in the last three days, six sites chosen by the Navy and six by the Air Force were given special attention.
The assaults were delivered for the most part by the Typhoon and Spitfire Squadrons of Nos. 83 and 84 Groups. The targets were very heavily defended by light flak and to attack them 'demanded great skill and daring'. The losses in aircraft and pilots were very heavy. Of the many assaults made, Leigh-Mallory in his despatch selected three as worthy of special mention. There was that of 2nd June carried out by eighteen rocket firing Typhoons of Nos. 198 and 609 Squadrons on the Dieppe/Caudecôte station, used for night fighter control and the control of coastal batteries. For the loss of one Typhoon, the station was put out of action. There was the attack on the 4th June on the station at Cap d'Antifer by twenty-three Spitfires of Nos. 441, 442 and 443 Squadrons Royal Canadian Air Force. They secured nine direct hits with 500 pound bombs and destroyed the 'chimney' and the giant Würzburg installations. There was finally the attack on the day before 'D Day' on the Jobourg station near the Cap de la Hague, attacked by Typhoons of Nos. 174, 175 and 245 Squadrons, firing rockets. It was equally successful.
Of the enemy's radar navigational stations, the two most important, one at Sortosville south of Cherbourg and the other at Lanmeur near Morlaix, were attacked, the first being destroyed, the second rendered temporarily unserviceable. Four wireless telephone stations of great importance were dealt with by Bomber Command. That at Mount Couple near Boulogne, made up of some sixty transmitters, was almost wiped out on the night of 31st May/1st June, seventy heavy bombs hitting the target, which was only 300 yards long and 150 yards wide. To make sure of this decisive result required the dropping of 474 tons of bombs by 105 Lancasters. That night, too, the station at Au-Fevre near Beaumont-Hague was rendered unserviceable, and two nights later the station at Berneval-le-Grand, close to Dieppe, was almost wiped out by 541 tons of bombs. The most important achievement, however, was the destruction by ninety-nine heavy bombers, dropping 509 tons of bombs, of the station at Urville-Hague near Cherbourg. This was the headquarters of the German Signals Intelligence Service in north-western France. The photographic interpretation report, afterwards found to be singularly accurate, stated that the station was completely useless, and the site itself rendered unsuitable for rebuilding. The destruction of this intelligence station had a powerful influence on the battle which began two days later, and was certainly one of the main reasons why the enemy's reaction in the air on 'D Day' and afterwards was so slight.
The results, then, of the air attacks on the radar stations were highly satisfactory. All six of the long-range reporting stations south of Boulogne were destroyed before 'D Day' and fifteen others in the area were made unserviceable. Thus large stretches of the Channel coast, as the vital day approached, were desolate of radar cover. By 'D Day', not more than eighteen per cent. of the enemy radar apparatus in north-west France was in operation, and for long periods of the fateful previous night, only five per cent.
The result was summed up by Leigh-Mallory in his despatch. 'The enemy did not obtain', he said, 'the early warning of our approach that his radar coverage should have made possible. There is, moreover, reason to suppose that radar-controlled gunfire was interfered with. No fighter aircraft hindered our airborne operations; the enemy was confused and his troop movements delayed'. Evidence subsequently discovered fully endorses this statement.