In 1943, British Naval Intelligence devised one of the most audacious deception operations of the war. They obtained the body of a recently deceased man, dressed him as a Royal Marines officer named "Major William Martin," and equipped him with fabricated documents suggesting the Allies would invade Sardinia and Greece rather than Sicily.
The body was released from a submarine off the coast of Huelva, Spain, where British intelligence knew a German agent operated. The Spanish authorities recovered the body and, as hoped, shared the documents with the Germans. Hitler himself was convinced and diverted significant defensive forces away from Sicily.
When the Allies actually invaded Sicily in July 1943, they faced considerably lighter resistance than expected. The operation, masterminded by Ewen Montagu and Charles Cholmondeley, is considered one of the most successful deception operations in military history. The true identity of the corpse remained a mystery for decades—it was eventually identified as Glyndwr Michael, a homeless Welsh man who had died from rat poison ingestion.