Operation Cornflakes was a World War II Office of Strategic Services PSYOP mission in 1944 and 1945 which involved tricking the German postal service Deutsche Reichspost into inadvertently delivering anti-Nazi propaganda to German citizens through mail.
The operation involved special planes that were instructed to airdrop bags of false, but properly addressed, mail in the vicinity of bombed mail trains. When recovering the mail during clean-up of the wreck, the postal service would hopefully confuse the false mail for the real thing and deliver it to the various addresses.
The content of the mail often included copies of Das Neue Deutschland, the Allies' German language propaganda news sheet. The postage stamps used on the envelopes were forged 6-pf and 12-pf Hitler-head stamps intended to look identical to genuine German stamps of the era, though these forgeries were printed by the OSS. In addition to these two forgeries, the OSS printed another design of the 12-pf stamp not-too-subtly redrawn so that Adolf Hitler's face shows his partially exposed skull. Also, the country identifier 'Deutsches Reich' (German Empire) read 'Futsches Reich' (lost, destroyed, or collapsed empire). Copies of this 'death head' stamp were inserted in the envelopes along with other propaganda materials.
The first mission of Operation Cornflakes took place on 5 February 1945, when a mail train to Linz was bombed. Bags containing a total of about 3800 propaganda letters were then dropped at the site of the wreck, which were subsequently picked up and delivered to Germans by the postal service.