"Early in the morning on the 1st of May 1943, a fisherman on a beach in Spain discovered a waterlogged corpse which had washed ashore during the night. The dead man was clothed in British military attire and a life preserver, and he had a briefcase chained to his lifeless body. Apparently a casualty of an airplane accident at sea, the body was transported to the local port, where its discovery was reported to the Nazi officials stationed in the city of Huelva...
Wary of a ruse, German intelligence examined the officer's personal effects in great detail. His possessions included numerous benign items such as a photograph and love letters from his fiancée, a set of keys, recently used ticket stubs for a theater performance, a hotel bill, etc. A close inspection and investigation strongly suggested that these items were genuine, indicating that Major William Martin and the documents on his person were authentic. A second letter in the dead man's possession– this one from the Chief of Combined Operations to the Commander-in-Chief in the Mediterranean– contained text indicating that Major Martin was carrying a letter too sensitive to be sent through normal channels, hence the need for him to fly.
By all appearances, the Axis powers had stumbled upon extremely valuable intelligence, unbeknownst to the Allies; a letter which indicated exactly which beaches the Axis powers would need to reinforce in order to repel the Allied invaders. The document discussed key details of "Operation Husky," a secret Allied plan to invade Nazi Europe by way of Sardinia, Corsica, and Greece. It also described a plan to prepare a false attack upon Sicily– the location where Germany expected the Allies to attack– as a way of drawing German forces away from the true invasion site.
Upon learning of the letter, Adolph Hitler took decisive action based on the information it disclosed. On May 12, he sent out an order: "Measures regarding Sardinia and the Peloponnese take precedence over everything else." He diverted significant defenses away from Sicily to the indicated points of hostile ingress, including an extra Waffen SS brigade, several Panzer divisions, patrol boats, minesweepers, and minelayers. But when the day of the attack came, all was relatively quiet on the beaches of Sardinia, Corsica, and Greece. The Germans had fallen for an elaborate deception designed to draw Nazi defenses away from the true Allied target: Sicily. Major Martin– the dead man the fisherman found on the beach– never existed..."