The unprecedented joint intervention by the United States and Japan to support the yen could fundamentally alter market trading behavior.
“Two sovereign economies simultaneously deploying increasingly scarce national assets to target the same objective forces the market to take notice of this power,” said Jesper Koll, an expert director at Monex Group.
The coordinated intervention to bolster the yen is historic and could reshape market trading logic. While Japan has intervened in currency markets on its own in the past, the scale of this action is far larger than usual. Reports indicate that the U.S. did not directly operate the USD/JPY pair but instead used the EUR/JPY cross-rate to implement the intervention, backed by clear political endorsement. Many investors view this as a landmark move.
Koll commented on the deterrent effect this creates for the market, stating, “The Japanese Ministry of Finance and the U.S. Treasury have successfully weaponized the yen.” He noted that this intervention goes beyond conventional foreign exchange management, as both countries are leveraging their government balance sheets to guide market expectations.
He added, “When two major sovereign economies, using increasingly scarce national assets, align their intervention toward a single target, the market has no choice but to respect that force.”
This joint intervention marks the first time the U.S. and Japan have bought yen together since 1998, and it is their first joint currency operation since the G7 coordinated to weaken the yen after the 2011 earthquake in Japan.
The political tool
Koll also pointed out that the political signal sent by this action is equally unprecedented. Washington and Tokyo are combining political support with financial firepower, placing the balance sheets of two major sovereign states against speculative capital, thereby raising the cost of shorting the yen.
Eswar Prasad, a professor at Cornell University, believes this is more of a defensive move, but it also marks a deepening integration of foreign exchange policy with geopolitics. “Foreign exchange market intervention has clearly taken on a geopolitical dimension,” Prasad analyzed. The Trump administration appears more willing to provide support to central banks of allied nations that are seen as aligning with U.S. strategic interests.
Some analysts compare this action to the U.S. support for the Argentine peso in the past. During the tenure of President Javier Milei, Argentina faced severe currency volatility shortly before a key midterm election. Between September and October 2025, the Trump administration rolled out a rescue package, using the Treasury’s Exchange Stabilization Fund (ESF) to provide a $20 billion currency swap line to the Argentine central bank and directly buying pesos in the open market.
Michael Gade, Chief Investment Strategist at Tactical Asset Management, said, “Bessent is the key figure throughout. It’s the same Treasury, the same ESF, the same strategy—using currency operations as a tool of statecraft. Supporting Argentina was essentially helping an ally.”
David Roche, an analyst at Quantum Strategy, similarly suggested that the U.S. motivation likely extends beyond maintaining financial stability and protecting the U.S. bond market; political considerations also play a role. “Trump might simply want to help his ally, Prime Minister Fumio Kishida, achieve his goals.”
The U.S. Treasury has not yet responded to a request for comment.
Where to begin
Strategists believe this intervention has already changed how investors view the yen. Billy Leung, Investment Strategist at Global X ETFs, said, “The core logic of the carry trade has been rewritten.” If investors realize that the risk of coordinated intervention is real, large-scale bets on yen depreciation will become more cautious, and capital will shift to other alternative funding currencies.
For a long time, the yen has been the world’s preferred funding currency for carry trades, where investors borrow cheap yen to invest in higher-yielding assets elsewhere.
Leung further elaborated on the deep impact: Currency policy risk, which had faded from view over the past decade, has now returned as a core market variable. If capital flows heavily into other funding currencies like the euro, the positioning structure of major global foreign exchange markets could be reshaped.
Ruyan Lu, Senior Fixed Income Strategist at State Street Global Advisors, agrees that traders will now have to incorporate more geopolitical variables into their pricing. “The biggest change is that traders now have a new pricing factor: the policy response function. They can no longer just look at macro fundamentals.”
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