Good story, and well worth the read:
On April 30th, 1943, a Spanish fisherman discovered the body of Major William Martin, a British Royal Marines courier. There was a briefcase attached to the dead man's wrist, which contained personal correspondence and documents related to the impending Allied invasion of Sardinia, in Greece. Spanish authorities notified the Germans, who moved quickly to fortify the Greek coast, leaving Sicily almost completely undefended. This was exactly what the Allies had intended.
"Major Martin," also known as "The Man Who Never Was," was an unwitting player in one of the greatest military hoaxes of World War II. The Allies had been planning an invasion of Sicily (and not Sardinia) for some time. Sicily, however, is mountainous, and therefore easier to defend than to attack. It is also so strategically located that the Germans were almost definitely expecting an attempt to dislodge them from it. And the buildup of troops and equipment that would be necessary for the invasion were certain to attract attention. If "Operation Husky," as the invasion was known, was to be a success, rather than a slaughter, the enemy's command must be led astray. Squadron Leader Sir Archibald Cholmondley, of the British Intelligence interservice XX Committee (XX for double cross) suggested that a set of false plans should be planted on a dead man, who would deliver them into the enemy's hands. This obviated any concern that the chosen spy could turn out to be a double agent, as well as ensuring that he wouldn't break under torture and confess whatever he knew about the true nature of his mission. Cholmondley entrusted the details of the mission to Lieutenant Commander Ewen Montagu of Naval Intelligence.
It was Montagu's idea that "Martin" should appear to have drowned, probably after his plane crashed off the coast of Spain. This necessitated finding a corpse whose lungs were already full of fluid, so that any doctors who examined the body would accept that he had been at sea for some time. He found a 34-year-old man who had recently died of pneumonia brought on by ingesting rat poison. The man would have been dead for some time before he fell into enemy hands, but the effects of salt water upon the corpse would disguise the inevitable decomposition. Intelligence secretaries pitched in to write love letters to "Martin," and one of them even donated a picture of herself in a swimsuit--ostensibly a photo of the dead man's fiancee, Pam. Cholmondley carried the letters in his wallet for several weeks, to give them an authentically worn appearance. "Martin's" personality was further enhanced by an irate letter from his bank manager, a stern letter from his father, a few overdue bills, a replacement military I.D. card, matchbooks, theatre tickets, keys... All the personal detritus of a likable young man who might be somewhat careless in his personal affairs (and thus more likely to wind up face-down on a beach in Spain), but who was doubtless quite good at his job. These items went into the briefcase with the documents that told of the Allies' plans to invade Sardinia.
"Operation Mincemeat," as Cholmondley had dubbed his master plan, was well under way. All that remained was to escort poor "Major Martin" into enemy territory. The body was packed in dry ice, and put aboard the British submarine HMS/M Seraph, under the command of Lieutenant Commander N. A. "Bill" Jewell. Just off the port of Huelva, Lt. Jewell said a short prayer, and Seraph gave "Major Martin" into the arms of the sea.
The discovery of the body didn't end the charade. The Allies were well aware that the Abwehr (German intelligence) would be watching them closely. Britain demanded that Spain return "Martin's" briefcase; after the requisite amount of diplomatic posturing, they did. It appeared to be untouched, but microscopic examination of the contents revealed that they had been carefully studied. "Martin" himself was buried in Huelva, with full military honors. His grieving fiancee sent flowers to adorn his grave. (And up until 1994, someone came regularly to lay red carnations there, but no one ever saw who it was.) On June 4, The Times included his name in the casualty lists. The Germans were completely convinced. Within days of "Martin's" appearance on the Spanish coast, Montagu telegraphed Winston Churchill to say "Mincemeat swallowed whole." On May 12, Adolph Hitler sent out an order: "Measures regarding Sardinia and the Peloponnese take precedence over everything else." He sent a Panzer division to Greece from France, ordered two Panzer divisions in Russia to prepare to move to Greece as well (and this just before the great tank battle at Kursk), and moved an extra Waffen SS brigade into the area. He thought he was well-prepared.
On July 9, 1943, the Allies moved. They concentrated their assault on the southern tip of Sicily, well away from the troops massed at the northern end, facing Sardinia. The Italian divisions collapsed almost immediately. The Germans, under Field Marshal Albert Kesselring, fell back to Messina. They resisted as well as they could, but Hitler still had it in his mind that the real attack would be in Greece, so they were not reinforced. On July 23, in fact, Hitler ordered Field Marshal Erwin Rommel to oversee the forces protecting Sardinia. By August 17, General George S. Patton and Field Marshal Bernard Montgomery had taken Sicily, due in large part to the efforts of a man who was dead before his mission even began.
Note: For many years, the true identity of "Major Martin" remained a mystery. He was known only as a man who had died of pneumonia in the winter of 1943. According to some reports, his family had requested that his name be kept a secret when they gave permission for his body to be used in Operation Mincemeat. Then Roger Morgan, a British town planning officer and amateur historian, discovered evidence that "Martin" was actually a homeless Welsh alcoholic named Glyndwr Michael, who had either committed suicide by eating rat poison, or been accidentally poisoned while sleeping in a barn.Two arguments support Morgan's theory. First, cyanide, a common ingredient in rat poison, causes pulmonary congestion, or chemical pneumonia. Second, when the British were constructing "Martin's" identity, they gave his place of birth as Cardiff, in Wales. It seems likely that "Major Martin" has indeed been identified.