The Crucial Deception
Bernard Montgomery, the British general who commanded the ground forces during the invasion, worried that the German army usually met an attack with a counter-attack and that powerful units of the German army, particularly the 21st Panzer (armored) Division, were only a few miles from the landing beaches. So it was absolutely clear to the invasion planners that the landing forces had to get ashore with minimal opposition. General Frederick Morgan, the Britisher who directed invasion planning, later wrote that "the ultimate aim [was] that the eventual blow would come where the enemy least expected it, when he least expected it, and with a force altogether outside his calculations." In a word, Morgan's "ultimate aim" was deception.
The Germans maintained a large intelligence organization called the Abwehr to learn where, when, and in what strength the invasion would occur. Its sources were photo-reconnaissance, cryptographers, captured documents, spies in Britain and elsewhere, British newspapers and radio, informants in European resistance movements, and prisoners-of-war, including Allied airmen shot down over occupied Europe. For their part, the deceptionists sought to mislead the Abwehr with bogus or inaccurate radio reports, visual displays of mock equipment, fake port facilities and military installations, gossip in neutral embassies, deliberate leakage of alleged confidential information, and, of course, double agents.
In the invasion, the Germans were completely surprised when the Allies sent the largest naval and air forces ever assembled-5,333 ships and 10,500 airplanes-across 100 miles of stormy sea and sky to Normandy on the night of June 5, 1944. This mighty armada was at sea for three days and remained unknown to the enemy until it appeared in the mist of morning light off Normandy's coast. Yet, even then, the Germans did not believe it represented the "real" invasion. Walter Warlimont, a German general stationed in Hitler's headquarters, wrote in his memoirs that staff officers "had not the slightest idea that the decisive event of the war was upon them." The Normandy invasion was a complete tactical and strategic surprise. The bad weather which caused Eisenhower to delay the invasion for one day explains the tactical surprise, but the fact remains that the Germans were surprised at every level of command. The German situation report on June 5 stated "Invasion not imminent." By the end of the next day, 176,000 Allied troops were ashore in France.
Surprise depends on concealment, or "security." But it was not enough for Allied planners merely to conceal their intentions and strength. Success in Normandy depended heavily on the Germans believing the real invasion was coming elsewhere. Eisenhower approved the deceptionists' proposal to reinforce the German prejudice that the "real" invasion was coming in the Pas de Calais. Not only must the Germans believe the deception; they must do something quite specific. They must keep the bulk of their forces clustered round the Pas de Calais rather than Normandy before, during, or after the invasion for as long as possible. Hitler himself was the ultimate target of the deception effort because from 1941 onward he made operational as well as strategic decisions, imposing his will at the battlefield level. Victory could hinge on deception that required both good security (concealment) and good intelligence (information) about what the Germans were thinking and doing.
Fortunately, the Allies had advantages in intelligence and security that may be unique. Unknown to the Germans, the British-led by Cambridge University mathematicians-were decrypting some German ciphers encrypted with the Enigma machine considered unbreakable by the Germans. This was the Ultra Secret, and the information obtained was called Ultra. British cryptographers broke the Abwehr cipher in December 1941 and read it to the end of the war. This provided an irreplaceable running check on how German intelligence was reacting to the deception-generated misinformation, Allied developments of which they were or were not aware, their worries, intentions, and beliefs. With Ultra, the Allies could overhear the Abwehr talking to itself.
A second intelligence advantage came from the Americans who had broken the Japanese diplomatic cipher before the war and eavesdropped on their radio messages throughout the war. Messages from Baron Oshima, the Japanese ambassador to Berlin, to his foreign ministry in Tokyo were particularly useful. When Thomas E. Dewey, the Republican challenger to President Roosevelt in 1944, seemed prepared to make a campaign issue of Allies' codebreaking advantage as it related to the Pearl Harbor disaster, General George C. Marshall, the head of the U.S. Army, sent him a secret letter saying that, "...our main basis of information regarding Hitler's intentions in Europe is obtained from Baron Oshima's messages from Berlin reporting his interviews with Hitler and other [German] officials to the Japanese government. These are still in the codes involved in the Pearl Harbor events." Oshima spoke frequently with Hitler or other top Nazis and inspected their defenses. He obliged the Allies by transmitting lengthy summaries that were sometimes read in Washington before they were read in Tokyo. In October 1943, for instance, after touring German defenses on the French coast, Oshima messaged home a description of what he had seen and heard, inadvertently giving the Allies their first overview of German preparations for the invasion.
If the Allies' intelligence was excellent, their security was superb. Wartime Britain was an island fortress under siege. The internal security agency, M.I.5, roughly analogous to the FBI, controlled the flow of information into and out of the country. Except for an occasional quick low-level flight across the Channel, German penetration of British air space after 1941 was mostly at the pleasure of the RAF, and the citizenry was vigilant about reporting suspicious behavior that suggested espionage. As for German agents, Ultra's ability to listen in on the Abwehr enabled M.I.5 to know when and where spies would be inserted into the country and to arrest them when they arrived, usually near their point of landing by parachute or submarine. With this extraordinary security, M.I.5 apprehended and controlled all German espionage agents in Britain.
It is a remarkable truth that every active German agent in Britain was located (about 120), taken into custody, and either converted ("turned") to work for the Allies or executed (seventeen) with the exception of one who was reprieved. The turned agents continued to communicate with their Abwehr masters but only communications that M.I.5 allowed them to send. Within M.I.5, the double agents were controlled by a small group called the Twenty (XX) Committee chaired by an Oxford don and future vice-chancellor, John Masterman (later Sir John). He labeled the systematic use of the double agents the "double-cross system." Always conscious that they were preparing for the day when the Allies returned to the continent, the Twenty Committee met weekly to decide what information could be safely conveyed to the Germans by the double agents. The goal was to build up the double agents' credibility by feeding the Germans plausible falsehoods as well as accurate information they either had or would obtain anyway, while giving away nothing vital. The double agents communicated with their Abwehr controllers by radio telegraphy, courier, mail, or personal contact.
A novelist and mystery story writer, Masterman was also a famed amateur athlete, having represented England in tennis, hockey, and cricket. Now he was a pivotal player in the high stakes game of the century. His shrewd fiction-plotting may explain why he was drafted for the "XX" Committee, which managed the complex manipulations of the double agents. After the war, Masterman would rightly claim for the double-cross system that "for the greater part of the war we did much more than practice a large scale deception through double agents; by means of the double-cross system we actively ran and controlled the German espionage system in [Britain]."
The double-cross system originated in the late 1930s almost by accident. Arthur Owens, a Welsh electrical engineer and civilian employee of the navy, was contacted by the Abwehr while traveling in Germany. Owens pretended to be receptive and accepted a radio from them. When he returned to England, he reported his contact to M.I.5, which responded by confiscating his radio and putting his name on the list of suspects detained when war broke out in September 1939. Owens then agreed that the radio should be used to reestablish contact with the Abwehr under the direction of M.I.5. His prison warden, an amateur radio operator, became his supervisor. Owens made contact with the Abwehr in Hamburg. The Germans welcomed the dialogue with Owens and put the first double agent into operation. After giving Owens the codename of Snow, the British followed with names for the double agents that ring like bells-Balloon, Bronx, Brutus, Careless, Carrot, Dragonfly, Lipstick, Mullet, Mutt and Jeff, The Snark, Sniper, Teapot, Tricycle, and Zigzag.