As the 70th anniversary of the D-Day landings at Normandy approaches, you will no doubt read stirring accounts of the bravery and heroism of Allied troops that were involved. You’ll read about the logistics miracle that made the landings possible as well as the subsequent thrust into France. There will be articles about the planning that went into the attack (out the window when so many units failed to land on their designated stretch of beach), and the turn of the weather upon which Operation Overlord depended.

But before the 5,000 ships, 13,000 aircraft, and 160,000 men steeled themselves for combat as they approached the Normandy coast, the battle — and probably the war — had already been won.

A gigantic deception was being perpetrated on the German army by the most colorful cast of characters ever tasked with winning a war. Double agents, con men, British noblemen, radio operators with a sense of humor, and, finally, the most colorful soldier of them all: General George S. Patton.

The deception — known as Operation Bodyguard — had a dozen different elements each designed to further the basic goal: confuse the Germans about where the landings would take place, keep them guessing about how many troops were engaged, and mask the actual date of the assault. “Bodyguard” was chosen as a name for the operation based on one of Winston Churchill’s most famous quotes: “In wartime, truth is so precious that she should always be attended by a bodyguard of lies.”

Deception had attended every major Allied landing up to that time, and we were getting very good at it. Part of the reason was that the British had broken some high-level German army codes and were able to read some of what the Nazi plans were. But for two years prior to D-Day, the British and American spymasters had come up with several gimmicks that were destined to flummox the Germans on the lead up to D-Day.

It all began with Operation Double Cross — the capture of most of the German spies in England and their transformation into the most effective double agents in Europe. The operation was run by MI5 and was overseen by the Twenty Committee chaired by Sir John Cecil Masterman, who would go on to become vice chancellor at Oxford. Masterman designed an intricate plan that had the double agents feeding disinformation to the German army intelligence organization known as the Abwehr. Most of it was useless — or even fanciful, like reporting that the British had developed electric canoes — but there was just enough truth in the reports to get the Abwehr to place great faith in their spies. By June 1944, that confidence in their intelligence would be their undoing.

Essentially, Operation Bodyguard was the overall designation for a series of smaller operations. The most important of these was Operation Fortitude South, where, with spectacular panache, British intelligence built an entire American army out of nothing — First Army Group South, or FUSAG. Using deception techniques honed in Sicily and North Africa, fake radio traffic was generated, dummy rubber landing craft, tanks, and planes were placed in plain view, “leaks” to diplomats were generated, and having General Patton, who the Germans were convinced would command FUSAG and lead the invasion, show up in a variety of locations to keep the Germans guessing about where the main thrust of the invasion would take place.

All of this disinformation was regularly “confirmed” by the Abwehr‘s trusted spies in England, who were following the orders of the Twenty Committee.

Perhaps Fortitude’s most notable success was convincing the German high command that the invasion would take place at Pas-de-Calais and not Normandy. Reading German wireless messages, the allies discovered that the German army believed that’s where the invasion would occur anyway, so it was easy to feed into their expectations.

Other elements of Bodyguard were designed to freeze German garrisons in Greece, the Adriatic, Norway, and the Bay of Biscay in France. The more troops they could pin down elsewhere, the fewer  could be rushed to Normandy in the days following the invasion. The Nazis already outnumbered Allied forces considerably in France and hiding the actual invasion site for as long as possible was paramount in order to give General Montgomery, the overall commander of the invasion forces, time to build a broad front.

Indeed, the plan worked to perfection. Fully seven weeks after the Normandy landings, Hitler and Reich Main Security Office  (who had destroyed the Abwehr in 1943) were insisting that the D-Day landings were a diversion and the blow would fall on Pas-de-Calais. By the time the German army realized their mistake, it was too late.

One final deception was carried out by the U.S. Army Air Force in the days leading up to the invasion….