What did Cincinnati's U.S. Playing Card Co (also known as the Bicycle Brand) send to GI's in Vietnam?
Answer: Decks of only the ace of spade
Here's why compliments of Gizmodo:
"During the Vietnam War, American soldiers started hearing rumors that the Vietnamese were very superstitious about the ace of spades. So Cincinnati's U.S. Playing Card Co. responded by printing decks of nothing but ace of spades—and sending them for free to GIs in Vietnam for the purposes of "psychological warfare."
Colin Dickey, author of Afterlives of the Saints, brought this fact to my attention on Twitter, where he links to a site that still sells the Bicycle 52 ace of spades deck. Supposedly the Vietnamese saw the ace of spades as a "deadly omen."
The Bicycle brand deck was particularly prized because it had two symbols of bad luck: The ace of spades and a woman printed on the back. The military's Stars and Stripes newspaper had claimed that the Vietnamese also considered seeing a woman before battle as bad luck. American troops started to leave the ace of spades on the bodies of people they'd killed and scatter the cards in fields when they were out on patrol."