Yesterday we honored the 70th Anniversary of Operation Neptune/Overlord, better known as D-Day, or the Invasion of Normandy.
Operation Neptune referred to the naval portion of the attack, while Overlord was the name for the ground operation.
But as momentous as D-Day itself was, as Cornelious Ryan famously tagged it, The Longest Day, the landings were only the beginning of what would become a massive campaign.
The Allied leadership, Eisenhower, Montgomery and Bradley, were quite confident the initial landings would be successful. The attacker has the advantage of choosing the time and place of the assault. To them, there was really no question that they would have a toehold on most if not all of the five beaches by the end of June 6.
The real question was, could they continue to reinforce and expand that beachhead? The initial allied assault was five infantry divisions and three airborne divisions. While they outnumbered the German forces in the immediate vicinity of the beaches on June 6, the Germans in northern France had two entire field armies. The struggle would be to see who could reinforce their units at the fight faster. Allied airpower worked The Transport Plan to prevent the Germans from quickly reinforcing the units on the coast.
The Allies were prepared to build up quickly enough to defeat the German 7th Army in Normandy, if only barely.
The problem was, the powerful German 15th Army was guarding the Pas de Calais. As soon as it became evident that the Allies would not conduct a landing there, it could be shifted south to join the 7th Army and overwhelm the Allied beaches.
The key became delaying that shift for as long as possible.
And that’s where Fortitude came in.
Fortitude was the code name for one of a series of deception operations designed to confuse the Germans. Under the overall plan named Bodyguard, initially the plan led the Germans to consider landings in such disparate places as Greece and Norway. As the build up of D-Day forces in Britain made it clear that northern France would be the target, the plan shifted to convincing the Germans that landings would come at Pas de Calais. Pas de Calais, at the narrowest point of the English Channel would have been the most obvious place to land. And that’s why the coast there was more heavily defended than anywhere else. Consequently, that’s why the Allies chose not to land there, choosing instead the Cotentin Peninsula in Normandy.
The Allies had wargamed the invasion of Normandy time and again (in fact, the Command and General Staff School in the US used a possible assault there as the core of its abbreviated syllabus during the war). Time and again they saw that if they could pin the 15th Army in Pas de Calais for 14 days, the build up would be strong enough to succeed. Fortitude sought to buy the Allies these critical two weeks.
Fortitude was actually two operations. Fortitude North used a fictional British 4th Army in Scotland to threaten an invasion of Norway. By means of fake radio traffic simulating the units of the 4th Army, and by double agents, Fortitude North actually lead to an increase in the number of German divisions in Norway, troop that otherwise might have gone to reinforce France (or the Eastern Front for that matter).
Fortitude South was designed to convince the Germans that the landings in Normandy were a diversionary attack, albeit a really big one. To sell Fortitude South, the Allies created the fictional First United States Army Group (FUSAG), notionally under the command of LTG George S. Patton. Patton had been relieved by Eisenhower in Italy, and if he wasn’t quite the golden-haired boy of US generals, he certainly held outsized sway in the minds of the German leadership, particularly Rommel. After all, he’d been the leader of the US invasions in North Africa and Sicily.* Choosing him to lead the invasion of Europe certainly seemed plausible to the Germans.
Fortitude relied on convincing the Germans that the Allies have far, far more troops and equipment in England than they actually did.
Four primary means would be used to build this illusion:
- Radio deception- by creating dummy radio traffic mimicking real units, the Allies allowed German intelligence to intercept traffic, and begin building an order of battle of FUSAG.
- Double agents- the XX Committee had captured and turned virtually every German agent in England. These double agents were carefully controlled to build their credibility with the Germans. During Fortitude, they were seen by the Germans as virtually gold-plated sources.
- Visual decpetions- German reconnaissance airplanes were allowed to see troop buildups that strongly suggested an assault across the channel to the Pas de Calais. A huge array of inflatable tanks and trucks, tentage, dummy landing craft made from barrels, plywood and canvas served to reinforce visually what the Germans already sensed from their radio intercepts and double agents.
- Code breaking- the Allies had broken a considerable amount of the German codes and had a very strong capability to monitor German traffic. How did that help deception operations, you ask? Well that’s worth a little more discussion.
One of the great challenges of any deception operation is determining their effectiveness. If the enemy has smoked out the deception, he can lay his own trap.
The Allies, especially the British and expatriate Poles, had thoroughly compromised German radio communications. The Allies had achieved a closed feedback loop, where they were able to determine which deceptions were successful, allowing them to reinforce those fears, via the first three means, and to reduce efforts on less successful operations. By knowing what worked and what didn’t, the deceptions of Fortitude became ever more convincing to the Germans.
Fortitude was also a very integrated plan. All three of the primary means worked in coordination with one another. Further, other elements of the British and other Allied governments worked within the Fortitude framework to bolster the plan. BBC radio made announcements and broadcasts that could be perceived as intended for FUSAG or British 4th Army.
So wholly did Fortitude South flummox the German high command that not only did it succeed in pinning 15th Army down for two weeks, it had Hitler convinced for an entire seven weeks that Patton would come charging across the Channel to Pas de Calais. By the time the scales fell from his eyes, Operation Cobra and the great breakout from Normandy were at hand. Fortitude had secured the flank of the Allied invasion, succeeding far, far beyond its creators wildest dreams.
*Depending how you measure it, the assault on Sicily was actually larger than the assault on Normandy.