Where to start
The unprecedented joint intervention by the US and Japan to support the yen could profoundly reshape future market behavior. While Japan has intervened in currency markets before, the scale of this operation far exceeds past efforts. More critically, it received explicit public backing from the United States. Reports indicate the intervention was not conducted directly through the dollar-yen pair but via the euro-yen cross rate, accompanied by clear political support signals.
Some investors believe this move carries significant weight. "The Japanese Ministry of Finance and the US Treasury have successfully weaponized the yen," said Jesper Koll, expert director at Monex Group, noting that this effectively serves as a deterrent to the market. He argued that the intervention has surpassed traditional foreign exchange management, as both countries are jointly deploying public balance sheets to steer market psychology. He added, "When two sovereign powers concentrate increasingly scarce national resources on the same target, the market has no choice but to take note."
This joint effort marks the first time the US and Japan have bought yen together since 1998, and the first coordinated intervention of this kind since the G7's 2011 action to weaken the yen following the Great East Japan Earthquake.
Why the political dimension matters
Koll also pointed out that this operation is unprecedented in its political signaling. By combining political support with financial firepower, the US and Japan aim to raise the cost of shorting the yen—placing two sovereign balance sheets on the opposite side of the trade. Eswar Prasad, a professor at Cornell University, described it as more of a defensive measure, but acknowledged that the move shows currency policy is increasingly intertwined with geopolitics. "Currency market intervention has clearly taken on a geopolitical tint," Prasad said, noting that the Trump administration appears more inclined to support central banks perceived as aligned with US priorities.
Some analysts draw parallels to US support for the Argentine peso under President Javier Milei. Amid currency turmoil ahead of a critical midterm election in September and October 2025, the Trump administration intervened with a support package, using the Treasury's Exchange Stabilization Fund (ESF) to conduct a $20 billion currency swap with the Argentine central bank and buy pesos in the open market. "Bessent is the key figure throughout. Same Treasury, same ESF, same playbook—using foreign exchange operations as a foreign policy tool," said Michael Gayed, chief investment strategist at Tactical Rotation Management. "Support for Argentina was about propping up an ally." Similarly, David Roche, a strategist at Quantum Strategy, said US motivations likely extend beyond financial stability or bond markets, with political considerations possibly playing a role. "He might just want to show goodwill to his ally, Sanae Takaichi." The US Treasury did not respond to requests for comment.
Market implications for investors
Strategists believe the intervention will change how investors think about the yen. "This will particularly alter the cost-of-funding logic in carry trades," said Billy Leung, investment strategist at Global X ETFs. "If investors now view intervention risk as a real and协同 threat, they are likely to be more cautious about large-scale yen shorting and may seek alternative funding currencies." The yen has long been the preferred funding currency for global carry trades, where investors borrow low-yielding yen to invest in higher-yielding overseas assets.
Leung added that the broader consequence is that "currency policy itself" has re-emerged as a source of market risk after a decade of dormancy. If investors gradually shift to other funding currencies like the euro, it could reshape positioning in major foreign exchange markets. Masahiko Loo, senior fixed income strategist at State Street Global Advisors, also believes the event means traders must increasingly incorporate geopolitical variables into their pricing. "The biggest change is that traders now have a new variable they must price in—the policy reaction function, not just macroeconomic fundamentals."
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