The Trout Memo, written in 1939, is a document comparing deception of an enemy in wartime with fly fishing

Fly fishing

Fly fishing is an angling method in which an artificial 'fly' is used to catch fish. The fly is cast using a fly rod, reel, and specialized weighted line. Casting a nearly weightless fly or 'lure' requires casting techniques significantly different from other forms of casting...

. Issued under the name of Admiral John Godfrey

John Henry Godfrey

Admiral John Henry Godfrey CB was an officer of the Royal Navy and Royal Indian Navy, specializing in navigation....

, Britain's director of naval intelligence, it was probably written by Ian Fleming

Ian Fleming

Ian Lancaster Fleming was a British author, journalist and Naval Intelligence Officer.Fleming is best known for creating the fictional British spy James Bond and for a series of twelve novels and nine short stories about the character, one of the biggest-selling series of fictional books of...

.

The memo reads, in part: "The Trout Fisher casts patiently all day. He frequently changes his venue and his lures. If he has frightened a fish he may 'give the water a rest for half-an-hour,' but his main endeavour, viz. to attract fish by something he sends out from his boat, is incessant." The memo goes on to describe numerous ways that the enemy, like trout, may be fooled or lured in.

One idea from the memo led to Operation Mincemeat

Operation Mincemeat

Operation Mincemeat was a successful British deception plan during World War II. As part of the widespread deception plan Operation Barclay to cover the intended invasion of Italy from North Africa, Mincemeat helped to convince the German high command that the Allies planned to invade Greece and...

, a World War II plan to convince the Germans that the Allies would attack Greece rather than Italy in 1943.