>I'll take "things that never happened" for $400
Operation Mincemeat was a successful British deception operation of the Second World War to disguise the 1943 Allied invasion of Sicily. Two members of British intelligence obtained the body of Glyndwr Michael, a tramp who died from eating rat poison, dressed him as an officer of the Royal Marines and placed personal items on him identifying him as the fictitious Captain (Acting Major) William Martin. Correspondence between two British generals which suggested that the Allies planned to invade Greece and Sardinia, with Sicily as merely the target of a feint, was also placed on the body.
https://en.wikipedia.org/wiki/Operation_Mincemeat
https://en.wikipedia.org/wiki/Military_deception
Peninsula campaign
John B. Magruder, Confederate general whose deceptions prevented a Union attack early in the war
In the American Civil War's Peninsula campaign, Union commander George B. McClellan was the victim of a deception executed by the forces under Confederate commander John B. Magruder during the 1862 Siege of Yorktown. Magruder, who had acted in and produced plays, used his knowledge of visual and audio effects to deceive McClellan into believing Magruder's force was larger than it was. These included placing straw dummy crewmen alongside Quaker guns—logs painted black to resemble cannons—in his defensive works. Magruder interspersed his Quaker guns with the few real cannons he possessed, making his artillery seem more numerous than it was. In addition, he used shouted orders and bugle calls to march his relatively small force of about 10,000 in front of Union positions until they were out of sight, then had them loop around unseen and march through the same area again, making his troop strength seem greater than it was. Magruder's elaborate charade convinced McClellan, who outnumbered Magruder by ten to one, that he faced a more formidable opponent than was actually the case, which caused him to delay attacking. McClellan's delay allowed Confederate reinforcements to arrive, causing him to retreat back to Washington, D.C.