I was wondering... in war, why not just print a load of enemy cash and drop it over their border?
I did a search but it was only used for propaganda during WW II:http://www.psywarrior.com/WWIIAlliedBanknotes.html
...rather than for full debasement.
Some highlights from the article though:
The British were attacking and attempting to undermine this military currency because they knew that by regulation these notes were issued strictly to the armed forces. The notes were valued at ten times their face as long as they were used in a military establishment. If a soldier tried to use the note in the local civilian economy it was worth only face value. Thus, if he tried to go on the black market or purchase illegally outside of the military canteens and barracks he suffered a 90% loss. This unusual method was a safeguard against the general public attempting to acquire and use the military currency. It worked well for the German economy, but made an easy target for the British propagandists.
The original idea came from the Political Intelligence Department, but the technology and printing was done by a private firm under the strictest security. The printing staff put 5 percent by quantity into bombs already loaded with newspapers and/or leaflets so that a drop of one million units of propaganda would have fifty thousand 50-pfennig notes included. When supplies ran out, a phone call to PID would mysteriously produce further parcels of banknotes delivered from nowhere on the backs of nondescript lorries.
These propaganda notes are punched with a small hole. This hole was used to run a fuse to a balloon. The notes were sometimes floated over France, and the slow-burning fuse released them over a wide area.
Under the code name “Grenville” SOE in London printed large amounts of Japanese military currency for the use of agents in the field in the Far East, and for the intended purchase of rubber and other essential commodities
on the Central Reserve Bank of China 50 cents note of 1940 they dispersed the English letters "C G W R S." The letters allegedly represent "Central Government Will Return Soon."
^hmm, we can't say that for sure though can we?
Sometimes the Chinese were less subtle. Three Federal Reserve Bank of China notes depict Confucius allegedly making an obscene finger gesture while striking a typical pose with folded hands. This vignette was later revised, so there may be some truth to the story. The note is actually known as "The Vulgar Wiseman" by collectors
We should add that true students of PSYOP will remember when something similar occurred about 30 years later. In 1968 North Korea captured the United States Navy vessel Pueblo. The crew was put on display as part of North Korea’s propaganda campaign to show the guilt and sorrow of the "criminals." Three of the crewmen in the front row showed their resistance to being used in anti-American propaganda by making a symbolic (half-victory sign) gesture with their finger.
Also from http://www.psywarrior.com/Vietnambanknote.html
Three British pacifists managed to sneak into the Air Force Base at Wethersfield in the United Kingdom in summer 1966. The young men eluded the security officers at the Strategic Air Command base and commenced to hand out leaflets to the passing airmen. These handbills were excellent reproductions of United States one dollar bills. One hundred thousand copies of the fake banknotes were produced. The printer was found and charged with forgery. Ten thousand copies of the banknote were mailed to the United States but the Federal Bureau of Investigation intercepted the shipment and confiscated them all.