VideoMark MossMark Moss

He Made $1 Billion Shorting The Yen. Now He's Trying To Save It

Japan’s efforts to support the yen have expanded sharply, but the intervention’s effect proved temporary as the currency remained near a 40-year low. Mark Moss argues that Japan’s heavy debt burden limits its ability to raise rates, while U.S. facilities such as the ESF and FIMA repo could provide additional support and liquidity. The discussion also examines the unwinding carry trade, the risks of weaker Japanese demand for U.S. Treasuries, and the potential effects on global borrowing costs and asset valuations.

CurrenciesMonetary PolicyGovernment DebtMarket LiquidityInterest RatesGeopolitical Risk

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Key Takeaways

Japan’s yen defense expanded from 5.6 trillion yen in October 2022 to nearly 8.5 trillion yen, or about $60 billion, in July 2026, yet the effect lasted only about five trading sessions before a jobs report reversed nearly all of it. Moss argues that Japan’s roughly 236% debt-to-GDP ratio limits its ability to raise rates substantially, making currency weakness and reduced purchasing power the preferred alternative to sharply higher debt-service costs.

The episode presents currency defense as a tradeoff between imposing higher borrowing costs on households and allowing depreciation to reduce the purchasing power of existing currency, illustrated by Britain’s 1992 rate increases from 10% to 15%. Moss argues Japan faces a similar constraint because defending the yen with higher rates would be especially costly given its debt burden.

Potential official support for the yen and global dollar funding relies on several limited channels: Moss estimates the Exchange Stabilization Fund has only about $43 billion available after accounting for special drawing rights, while the FIMA repo facility has a $60 billion cap and reached that limit in 2023. He identifies renewed usage of foreign-official repos in the Fed’s H.4.1 report—after eight consecutive weeks at zero—as a signal that intervention or emergency funding needs may be accelerating.

DEBT-MARKETS

Duration Mismatch — Moss explains the 2023 bank failures through a duration mismatch: banks funded long-term Treasury holdings with deposits that could be redeemed on demand. When the Federal Reserve raised rates rapidly, Treasury values fell, forcing banks to sell bonds at losses as depositors withdrew funds.

“Why? Well, because they had a mismatch on duration. They took in customer deposits. Customer deposits are due on demand…”—

Carry Trade — Japan’s carry trade relied on borrowing at roughly 0% to 1% in Japan and investing in U.S. Treasuries yielding about 4% to 5%, creating a spread near four percentage points at the low end. That spread narrowed from roughly 4% in October 2023 to less than 2% as the Bank of Japan raised rates five times to 1%. Moss says the shrinking gap is prompting traders to unwind positions and contributing to currency moves.

“So, I borrow low, I borrow at 1% and I put it into something making 5% and I make a 4% spread, right?…”—

Debt-Yield Gap — Moss argues that Japan’s bond-market pricing appears inconsistent with its debt burden: Japan has about 220% debt-to-GDP but pays roughly 3.9% on 30-year bonds, compared with the United States at about 120% debt-to-GDP and a 5.25% rate. He suggests Japanese borrowing costs could eventually move toward the relationship implied by debt levels, while emphasizing that the chart is not a forecasting tool.

“On the other end, well, we have the United States five and a quarter and about 120% debt-to-GDP. United Kingdom, Euro, Canada are in in between that…”—

LIQUIDITY-FACILITIES

ESF Firepower — Moss estimates that the Exchange Stabilization Fund has about $217 billion in total assets, but roughly $172 billion is already tied to special drawing rights. That leaves approximately $43 billion as a net position potentially available for intervention.

“Now, this is as of June 30th of this year. And what this shows us is that there's about 217 billion in total assets to stabilize exchange rates…”—

FIMA Backstop — The Federal Reserve’s Foreign and International Monetary Authority repo facility allows approved foreign central banks, including the Bank of Japan, to pledge U.S. Treasuries temporarily in exchange for dollars. By providing collateralized emergency liquidity, it helps institutions meet dollar needs without forcing abrupt Treasury sales into the open market. The facility is intended to calm global dollar shortages and reduce disruptive pressure on U.S. government debt.

“The FEMA is the foreign and international monetary authority repo facility. So that's the FEMA foreign international monetary authority…”—

YEN-POLICY

Yen Defense — Japan’s yen defenses have grown sharply, from 5.6 trillion yen in October 2022 to nearly 8.5 trillion yen, or about $60 billion, in July 2026. Tokyo began intervening on July 30, with the United States joining the following day in its first yen-support intervention since 1998. Despite the effort’s scale, the defense lasted only about five trading sessions before a jobs report reversed nearly all of its effect, while the yen remained near its weakest level in roughly 40 years.

“Now, last month, $87 billion was spent in just two days…”—

Black Wednesday — Mark Moss uses Britain’s 1992 Black Wednesday crisis to illustrate the tradeoff involved in defending a currency. The Bank of England raised rates from 10% to 12% and then 15%, intensifying pressure on households with variable-rate mortgages. Authorities could impose greater costs on homeowners and consumers to preserve the pound or allow depreciation, which reduces existing currency’s purchasing power and makes prices appear to rise.

“And what was happening is as Britain, as the Bank of England was trying to protect their pound, they kept raising prices. So, at 9:00 a.m…”—

Yen Defense Begins

Mark Moss introduces Japan’s currency crisis, the record intervention supporting the yen, and why the defense matters for U.S. Treasury yields and household borrowing costs.

Record Yen Intervention

Tokyo and Washington intervene together for the first time since 1998, but an $87 billion defense is quickly overwhelmed by economic data and continued yen weakness.

Bessent’s Currency Playbook

Moss explains Scott Bessent’s role at Treasury and revisits his billion-dollar trades against the pound and yen to illustrate how governments choose between currencies and debt markets.

Japan’s Debt Dilemma

The discussion connects Japan’s 2013 devaluation and enormous debt burden to Bessent’s strategy, arguing that governments typically sacrifice the currency rather than destabilize bond markets.

Exchange Stabilization Fund

Moss examines U.S. policy signals and the Exchange Stabilization Fund, concluding that its apparently large assets leave far less immediately usable foreign-currency ammunition than headline figures suggest.

FIMA Repo Backstop

The FIMA repo facility lets foreign central banks exchange Treasuries for dollars without selling debt openly, providing emergency liquidity while its $60 billion capacity remains a concern.

Carry Trade Unwinds

Japan’s low rates created a massive borrowing-and-investment spread, but Bank of Japan hikes and rising fiscal concerns are compressing the carry trade and driving broader currency volatility.

Treasury Buyer Risk

Japan’s debt and currency choices could reduce its demand for U.S. Treasuries, forcing the United States to offer higher yields that affect mortgages, credit, businesses, and asset valuations.

Watch The H41 Report

Moss identifies Thursday’s Federal Reserve H41 report as the key signal, explaining that rising foreign official repo usage would indicate the yen-support operation is accelerating.

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Important Disclaimers

Not Investment Advice: For education only — not financial, tax or legal advice.

AI-Generated: Made by AI from source transcripts and may contain errors.

No Guarantees: Past performance does not predict future results; investing carries risk.

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