Ruge's headquarters was in the Bois de Boulogne — a hundred yards away from Group West in Paris. Only his Chief of Staff, Captain Hagen, and his first operations officer, Cdr. Hugo Heydel, knew what was happening. Obviously Heydel could not continue to work in the general operations room in case the secret leaked out. But how could he leave it without starting gossip? Ruge devised a little plot. He told Heydel to complain that the clamour in the busy operations room made it impossible for him to concentrate. Then Ruge took up his complaint and arranged for him to exchange with an officer who had a private room. No one suspected anything and Heydel could get on with his planning in secret.
But Ruge faced a much greater problem of secrecy. This was that he could not hold an overall briefing conference with his captains nor order his mine-sweeping flotillas to sweep an obvious course. Instead he divided the route up into a jigsaw and directed his mine-sweepers to sweep individual sections. These individual pieces of the mine-sweeping jigsaw were plotted day by day by Heydel on a secret chart in his private room.
Ruge's other problem was finding suitable excuses for issuing his orders, in case his crews began to wonder why all this intensive mine clearing had started. Many pretexts had to be devised to enable him to make a complete sweep of the proposed route. False reports were concocted about British mine-fields as an excuse for sweeping German mines. These reports were given to the mine-sweeping officers and men as genuine operational information.
The orders given by Commodore Ruge to his flotillas were crystal-clear. He laid down that the Channel was only to be swept at night and time limits for each stage were to be punctually adhered to. But to the officers carrying them out in ignorance of the over-all picture the whole operation seemed bewildering and purposeless.
Although Ruge could not rouse his crews to enthusiasm for the task which they were doing, they carried it out with the utmost efficiency. During January, under cover of darkness, German mine-sweepers groped their way along the heavily mined route. Continual bad weather made their task more difficult.
On 25 January the destroyer
At the same time, destroyers and torpedo-boats needed to screen the battleships began sailing westward down the Channel. Their movements were made an excuse for some of the mine-sweeping operations required.
The next big question was how to mark the swept channel. Not only were buoys only possible for a short inshore part of the course but there were also dangers in placing more buoys outside Brest. In the first place they might be spotted by British reconnaissance. Also the tendency in those mid-war days was to remove buoys — and to anchor new ones might puzzle French port officials and cause suspicion.
To avoid this, Ruge arranged for some of his small mine-sweeping craft to anchor as 'mark-boats' along the most important points of the route, while the operation was in progress. When the captains of the mine-sweeping craft came to open their secret orders they were mystified. For each contained instructions to sail to a certain position in the Channel at a time laid down, and anchor there to act as a 'living buoy.' They had to endure the hazards of air attack with no idea of the vital importance attaching to their role. But no explanation was possible.
Meanwhile, based on Ruge's information, Admiral Saal-wachter's staff officers in Paris prepared the navigation charts. They were delivered to the ships in Brest by 'safe hand' officer messengers with the rank of naval captain. Yet in spite of the most careful planning, several of the mark-boats were off position on the day. But no operation, however well planned, can be perfect.
Next to mines, the greatest danger to the ships was the unseen eyes of radar stations strung along the English Channel coast. The Germans already knew from the reports of Captain Brinkmann of the
Even before the outbreak of the war they were curious about British radar. Then in the spring of 1939 350- foot aerial masts were erected from the Isle of Wight to the Orkneys, German Intelligence marked them down as radio transmitters. But General Wolfgang Martini, the Head of the Luftwaffe Signals Service, was not satisfied that they were.
He was suspicious of the fact that these latticed aerials were on different wavelengths from the crude German Freya and Wurzburg radars, which German firms were developing. Was this possibly more advanced radar than his own country had? At a meeting with German Air Force chiefs, Goring and Milch, Martini came forward with a startling suggestion. He suggested a Zeppelin reconnaissance. When Goring asked, 'Why not use an aeroplane?' Martini explained that only an airship could remain stationary in the air to record a series of signals. Goring ordered one of Germany's two remaining Zeppelins to be converted into an airborne radar spy.
One night in May 1939 the 776-feet long Zeppelin LZ 127 left Frankfurt and headed over the North Sea with aerials rigged underneath her gondola. She flew towards the Bawdsey Research Station at Orfordness, Suffolk, where tall masts could be seen. Aboard her was General Martini. While the Zeppelin cruised along the Suffolk coast technicians in her gondola manned special radio detectors. All they picked up was a loud crackling.
At Bawdsey, the radar operations staff gazed in astonishment at the largest 'blip' they had ever seen travelling slowly across the radar screen. They guessed correctly that it was a German airship carrying out radar investigation. As she flew along the east coast the Zeppelin picked up only more crackling in her receivers. General Martini landed in Frankfurt still as ignorant of the development of British radar.
A month before the outbreak of war — or 2 August 1939—the Zeppelin made a second trip. Her instructions were to keep fifteen miles off the east coast of Britain and note the wavelengths, strength and position of all high- frequency signals. Martini was not aboard this time but sent his senior officer, Lt.-Col. Gosewisch. Once again no transmissions were detected — and British radar did not pick up the airship.
But she was seen. Coastguards in Aberdeenshire reported her and two RAF fighters took off from Dyee and identified the airship. But she was well outside territorial limits as Martini had ordered.
She cruised near the British naval base at Scapa Flow, catching glimpses of British warships through the clouds before setting course back to Germany, again without detecting any high-frequency signals.
A month later, when war broke out, such Zeppelin cruises off the coast of Britain were impossible. In spite of the two abortive Zeppelin flights, General Martini was convinced that Britain was ahead in radar. He persevered in trying to find out more about their sets.
The fall of France in 1940 gave him his opportunity. Special teams of Luftwaffe and Navy signal experts were sent to the Channel coast to find out whether instruments similar to their radar had been established on the English south coast. Until then the Germans had no definite proof that the British were ahead. When these radar intelligence receivers recorded a number of English radar sets on meter and decimeter wavelengths, reconnaissance planes helped to pinpoint their locations for an exact map of all existing radar. From these precise observations, the Germans were able to deduce a good deal about the development of the British radar devices. Martini decided to jam them.
During the next year jamming stations were established in Ostend, Boulogne, Dieppe and Cherbourg. They were equipped with very efficient directional beam antennae, synchronized with the search impulses of the British equipment. They could achieve effective jamming from Cherbourg to the Isle of Wight. Several aeroplanes also had jamming equipment.
When told of Operation Cerberus, General Martini personally directed his 'interference' operations. At dawn each day during January English radar stations had a few minutes of jamming, deliberately made to appear like atmospherics. Every day the length of the jamming increased slightly. By February British radar operators were wearily accustomed to this interference. They reported it as 'caused by atmospheric conditions.'
This brilliant, painstaking radar plan was to play a decisive part in delaying the British defences.
The day after the New Year conference a staff car appeared on the quai Lannion. Ships' officers recognized the visitor it contained as the famous Battle of Britain fighter ace Col. Adolf Galland.
