|1942 Japanese Invasion Philippines Peso with a JAPWANCAP Stamp|
In January 3, 1942, a few weeks after successfully invading Philippines, the Japanese Commander-in-Chief announced that occupying forces would henceforth use military-issued currency as legal tender. Notes were to circulate at par with existing Philippines "Commonwealth" Pesos. Since this military scrip was not directly convertible into existing pesos, the trick to get it to circulate at par can probably be found in the tersely titled proclamation Acts punishable by death which, among seventeen acts that could result in loss of life, listed the thirteenth as:
(13) Any person who counterfeits military notes; refuses to accept them or in any way hinders the free circulation of military notes by slanderous or seditious utterances.This is a great example of a Warren Mosler fiat money. According to Mosler, the state's requirement that citizens discharge their tax obligation with a certain intrinsically worthless medium on pain of being shot in the head is sufficient to give that medium a positive value. Likewise, requiring citizens to use the same medium in the course of regular payments and accept it to discharge debts, all on pain of death, would probably have promoted a positive value for intrinsically worthless paper.
Over time, those bits of "forced" paper will enjoy constant purchasing power as long as the issuer withdraws excess currency or adds it when desired. This is the quantity theory of money.
By 1943, however, it seems that the Japanese occupying forces, now being pushed back by the Allied forces, were desperately issuing excess notes to pay for operations. The Filipino monetary system proceeded to run smack dab into Gresham's law. The unit of account, the peso, was defined in terms of two different media—original pesos and military pesos. This meant that debtors could choose to discharge their debts with either. However, if one was perceived to be more valuable than the other, this superior medium would be hoarded and the inferior one used to pay off the debt. Legacy pesos had completely disappeared from circulation by 1943—only war pesos were being used to discharge debts and pay for goods, a decent indicator that the value of Japanese invasion pesos had fallen below that of original pesos. Bad money had chased out the good. (See  and  for evidence of Gresham's law)
Through 1944 and 1945, the war peso would endure extreme inflation. 10P had been the largest denomination in 1942. The military introduced 100P, 500P, and 1000P notes in subsequent years. In Neil Stephenson's Cryptonomicon, a wide-ranging historical/science fiction novel filled with monetary themes, there's an interesting passage in which Japanese soldier Goto Dengo describes the use of military scrip, probably sometime in 1943 or 1944:
The owner comes over and hands Goto Dengo a pack of Lucky Strikes and a book of matches. "How much?" says Goto Dengo, and takes out an envelope of money that he found in his pocket this morning. He takes the bills out and looks at them: each is printed in English with the words THE JAPANESE GOVERNMENT and then some number of pesos. There is a picture of a fat obelisk in the middle, a monument to Jose P. Rizal that stands near the Manila Hotel.Japanese invasion currency, already being well on its way to being repudiated, would become completely worthless upon Japan's unconditional surrender in 1945.
The proprietor grimaces. "You have silver?"
"Silver? Silver metal?"
"Yes," the driver says.
"Is that what people use?" The driver nods.
"This is no good?" Goto Dengo holds up the crisp, perfect bills.
The owner takes the envelope from Goto Dengo’s hand and counts out a few of the largest denomination of bills, pockets them, and leaves.
Goto Dengo breaks the seal on the pack of Lucky Strikes, raps the pack on the tabletop a few times, and opens the lid.
Well, not entirely valueless. The second chapter in the life of military scrip begins with The Japanese War Notes Claimants Association of the Philippines, or JAPWANCAP. Formed in 1953 on behalf of Filipinos left holding stranded quantities of worthless Japanese invasion money, JAPWANCAP's mission was to hold both the US and Japanese government's liable for the redemption of war currency (the US had also issued counterfeit Japanese military currency). So while pesos had been valued prior to the war's end upon pain of death, and their value regulated by limiting the quantity outstanding, those same pesos were now valued on the margin as a liability of their issuer. Given the possibility of redemption, an old invasion note was worth more than zero.
Was JAPWANCAP successful? While the case was heard in a United States Court of Claims in 1967, it was thrown out on a technicality, the statute of limitations having had passed. Put simply, the court would not hear a claim that had not been filed within six years of that claim first being accrued, and in JAPWANCAP's case many more years than that had already passed.
This makes one wonder, if Filipinos in 1953 were already convinced that Japanese invasion pesos were the liability of the issuer, and therefore redeemable in some quantity of yen or dollars, did that same motivation also lead them to originally accept new military pesos in 1942? To what degree was the initial acceptance of pesos driven by the threat of force (& subsequent changes in value regulated by their quantity), and to what degree was their value dictated by their status as a liability of a well-backed issuer? That's a question we can never be entirely sure of. But while the force/quantity theory story fits the facts, the liability story does too. The military peso's inflation, for instance, can be attributed to the rising quantity of money, but also to the increasing likelihood of Japan losing the war, a loser's liability's being worth far less than a winner's.
Which brings us to the third chapter in the evolution of Japanese military pesos. Nowadays you can buy the notes on eBay for a few bucks. Their value is no longer dictated by gunpoint, nor by their liability nature, but their existence as a unique commodity, much like gold, bitcoin, or some rare antique.
To learn more, here is a paper called "Financing Japan’s World War II occupation of Southeast Asia"
Note: I will be posting sparsely over the next two months, probably once every two weeks.