| During World War II, the German Central Security Office undertook an operation with the intention to ruin Great Britain's economy through the counterfeiting British five pound notes.
Operation Bernard, as it was dubbed, aimed to produce around 100 million British pounds (1.5-2 billion dollars US today), and to send them to Britain. The transfer of the bogus money was to take place in several ways:
German secret agents in Britain were to covertly put the fakes into circulation by making large cash purchases
Money transfers through neutral countries such as Switzerland and kinda-neutral Spain
Luftwaffe air drops of the false notes across the British countryside
The plan was given to Germany's head document forger, Bernard Kruger (Bernard, what a co-incidence!), who was in charge of the forging of documents for Germany's secret service. Kruger began different groups working on the problem of replicating British bank notes. One group used photography to duplicate the design of the notes, while another tried to find the right paper (supposedly, the final paper was made from dirty Turkish rags), another team worked on the ink, and another team solved the problem of serial numbers.
With all the parts in place, Germany began the production of the counterfeit currency. The primary laborers in the printing of the false currency were concentration camp internees. Kruger apparently was in the business of employing as much concentration camp labor as possible, in order to spare them from the death camps and Nazi medical experiments.
After the printing process was canceled by his superiors, Kruger convinced them to allow him and his laborers to start counterfeiting United States dollars, which he did right up until the end of the war.
Operation Bernard never made any noticeable impact on the British economy, nor would it have, even if the full 100 million pounds had been printed. Most of the fake pounds were used to pay spies and the like, were found in crates at the bottom of lakes in Austria, and it is rumored that some Nazis used them to pay for their escape after the war.
Bernard Kruger's British pound counterfeits turned up as late as the 1960s. | 
