I like 'Operation Mincemeat'. It had everything — and it worked! The British are crafty like that, they like the cloak & dagger stuff, and they're good at it. The Allies were planning to invade Sicily; but they wanted the Germans to think they were going to go up through Greece. So they planted fake invasion plans for Greece on an already dead man, floated his body in the water off the southern coast of Spain — where they knew the Germans would get word of it — and the Germans read the plans and thought the Allies were going to Greece! Brilliant! Has anyone got any other cool deception plans regarding WW2?
Mincemeat was effective but pales when compared with Operation Fortitude: the D-Day Destraction. It was impossible to hide in early summer 1944 the pending invasion of western Europe by the American-Allied juggernaut. Aero-photography showed the massive stockpiles of men and machines. Stories leaked, some deliberately. Such was the case of Operation Fortitude. Allied Intelligence discovered through Magic (Japanese signal intelligence) that Adolf considered the invasion would come in the Pas de Calais region of the French coastline. After all, it was the closest point of England to France, maximizing Allied Airpower. To reinforce this idea Allied Intelligence created a fictional army commanded by the premier American combat commander: G.S. Patton. Rubber dummy-tanks and fake radio traffic comming from fake tent cities completed the illusion of another army ready to invade Pas de Calais. Fortitude was effective. Adolf withheld the transfer of units from Pas de Calais to Normandy far longer than was expected because of the implied threat of Patton invading at Pas de Calais.
Operation Bodyguard was a pretty good one. Heavily linked to the D-Day landings in June of 1944. Essentially the allies would give fake information and create fake armies as to displace the axis army and allow for a better chance of the D-Day landings to succeed. Reinforcements from the axis would be slow to come back to Normandy and heavily favoring the allies. You can look up more information on the operation here: http://gadabyte.com/ww-ii/bodyguard.html or http://en.wikipedia.org/wiki/Operation_Bodyguard
http://en.wikipedia.org/wiki/Ghost_Army This link has even more info/research about these types of operations. I really enjoyed how devious and deceptive most of these methods were. In war, nothing is sacred it seems.